# Write a code expression

> The Code calculation style — placeholders A–D, the keyword reference, and worked examples.

Source: CBX documentation, version 4.0 preview (unreleased). Canonical page: https://docs.configbox.at/docs/4.0-preview/admin-guide/pricing/write-a-code-expression. Last updated 2026-08-02.

---
> **Audience:** store admins · **Scope:** the Code calculation style · **Last reviewed:** 2026-07-21

**What this does** — Lets you *type* a pricing formula instead of assembling it from drag-and-drop
chips. It is the same engine as the Formula style with a different way in: quicker for short
arithmetic, and the only style that can read the running **total** of the configuration.

Despite the name, this is not programming. An expression is a line of school arithmetic —
numbers, `+ - * /`, brackets — where some of the numbers are written as keywords that CBX
replaces with live values from the customer's configuration.

## Before you start

- Read [where prices come from](https://docs.configbox.at/docs/4.0-preview/admin-guide/pricing/where-prices-come-from) and
  [build a calculation](https://docs.configbox.at/docs/4.0-preview/admin-guide/pricing/build-a-calculation) — a code expression is one of the three calculation
  styles, and is created, saved and attached exactly like the others.
- Have the **IDs** of the questions and calculations you want to read. Question IDs appear next to
  the title in the placeholder drop-downs (`Motor Power (ID: 2)`) and in the questions list;
  calculation IDs are in the **Calculations** list.
- If the formula only reads questions the customer types into, you may not need any keyword at all
  — the A–D placeholders will do.

## Steps

1. Go to **Calculations**, click **Add**, name the calculation, choose the **product** and pick the
   style **Code**.

2. Bind up to four questions to the placeholders **A**, **B**, **C** and **D** using **Question for
   placeholder A** … **D**. Leave the rest on **Not used**.

   ![The code editor: a threshold expression on placeholder A, chaining another calculation](img/calculation-code.jpeg)

3. Type the expression in the **Code** box. The screenshot's formula is an area price in
   square metres: two questions in millimetres bound to A and B, then

   ```
   A * B / 1000000 * 65
   ```

4. **Save**, then **attach it** — nothing is calculated until the calculation is set as a
   question's or answer's **Price Calculation** (or Recurring Price / Weight Calculation), used as
   a calculated minimum/maximum, or referenced from a rule or another calculation. See
   [build a calculation](https://docs.configbox.at/docs/4.0-preview/admin-guide/pricing/build-a-calculation).

5. Open the configurator and check the number against a calculator. Always check a code expression
   live — it is accepted as typed, without a preview.

## The three rules that break formulas

The editor's own **Notes** section states them, and almost every broken expression breaks one:

1. **A dot is the decimal mark.** `0.25`, never `0,25`.
2. **No thousands separators.** `1000000`, never `1 000 000` or `1,000,000`.
3. **A space before and after every placeholder and keyword.** `A * B`, not `A*B`. The values are
   substituted textually, so a missing space glues two numbers together.

Placeholders accept numbers only. Bind them to text-field questions with numbers-only validation,
and an empty field counts as `0`.

## Keyword reference

Every keyword is replaced with a live value from the configuration the customer is building.

| Keyword | Value it produces |
|---|---|
| `Total` | The running total of the configuration. **Once per product only** |
| `TotalRecurring` | The running recurring total. **Once per product only** |
| `QuestionPrice(id)` | The current price of that question |
| `QuestionPriceRecurring(id)` | The current recurring price of that question |
| `QuestionSelection(id)` | What the customer typed into that question — numbers only; empty counts as `0` |
| `QuestionProperty(id.path)` | Any attribute of that question or its selected answer (see below) |
| `Calculation(id)` | The result of another calculation of this product |

`QuestionSelection(id)` does exactly what an A–D placeholder does. Use the placeholders while you
have four or fewer questions — they read better — and fall back to the keyword beyond that.

### QuestionProperty paths

Write the question ID, a dot, then the attribute. Using question 22 as the example:

| Path | What it reads |
|---|---|
| `QuestionProperty(22.selectedAnswer.weight)` | The weight of the answer the customer picked |
| `QuestionProperty(22.question_custom_1)` … `_4` | The question's own custom fields (question screen → **Custom Fields**) |
| `QuestionProperty(22.selectedAnswer.assignment_custom_1)` … `_4` | The selected answer's custom fields, from the answer screen |
| `QuestionProperty(22.selectedAnswer.option_custom_1)` … `_4` | The selected answer's *global* custom fields, from the answer screen |

Custom fields are how you attach your own numbers — a material factor, a supplier code, a labour
rate — to a question or an answer and price from them, without inventing a hidden question.

### Reading the question you are attached to

`RegardingQuestion` means "whichever question or answer this calculation is attached to". A
calculation written with it can be attached to many questions at once and always reads its own:

| Keyword | What it reads |
|---|---|
| `RegardingQuestion(question_custom_1)` | Custom field 1 of the question using this calculation |
| `RegardingQuestion(regardingAnswer.weight)` | The weight of the answer using this calculation |
| `RegardingQuestion(regardingAnswer.assignment_custom_1)` | Custom field 1 of the answer using this calculation |

This is what turns ten near-identical formulas into one.

## Worked examples

**Area price.** Width and Height are text fields in millimetres, bound to A and B; the rate is €65
per square metre:

```
A * B / 1000000 * 65
```

**A percentage of the whole configuration.** Attach to the question that should carry the
surcharge — an insurance or service option, for instance:

```
Total * .25
```

The demo store's *Phone with Contract* product does exactly this, and the recurring twin
`TotalRecurring * .25` for the monthly side. Remember the once-per-product limit: only one
calculation in a product may read `Total`.

**Price from a custom field.** The material factor sits in custom field 1 of each answer of
question 30, and the base rate comes from a text field bound to A:

```
A * QuestionProperty(30.selectedAnswer.assignment_custom_1)
```

**Composing calculations.** Keep pieces small and readable, then combine them:

```
Calculation(14) + Calculation(15)
```

**Reusable per-question rate.** One calculation attached to every answer that carries a rate in its
custom field 1, multiplied by the entry in A:

```
A * RegardingQuestion(regardingAnswer.assignment_custom_1)
```

## Good to know

- **Code and Formula are equally powerful for arithmetic** — pick whichever *you* will still
  understand in six months. The one thing only Code can do is read `Total` / `TotalRecurring`.
- **Compose, don't inflate.** Several small named calculations referencing each other with
  `Calculation(id)` stay debuggable; one long line does not.
- **Watch the ID.** Keywords address questions by number, so a formula that reads
  `QuestionProperty(30…)` breaks silently if question 30 is deleted. The calculation edit form
  lists where a calculation is in use; there is no equivalent warning in the other direction.
- **Author in the base currency and ignore tax.** Currency conversion, customer-group overrides and
  tax are applied on top of the result.
- Copying a product copies its code calculations and re-points every reference.

## Troubleshooting

- **The price is 0 or blank.** A placeholder is bound to a question the customer hasn't reached, or
  to one that isn't numbers-only. Empty entries count as `0`, and anything multiplied by `0` is `0`.
- **The result is wildly wrong.** Look for a missing space around a placeholder, a comma used as a
  decimal mark, or a thousands separator.
- **`Total` gives a strange number.** Check that no second calculation in the same product also
  uses `Total` — it may be used only once per product. Also remember it is the total *so far*, so a
  percentage-of-total surcharge should sit on a late page.
- **Nothing calculates at all.** The calculation isn't attached yet. Creating it is only half the
  job — see step 4.