**Note:** If your rules screen looks different from the image below, click here.

The Value rule performs a simple calculation using values from other fields in the document.

**Example 1: **Calculate Extended Price1

To **Add** a **Value Rule**, select the **Rules** menu.

Select the field you wish to apply the rule to.

You will then **Select Value Rules**.

Select the type of value rule that you want to use, we will use the **Basic Math Function**.

Choose the fields that need to be multiplied: **Unit Price 1 and Quantity1**

Select the mathematical function needed: **Multiplication**

Every time the Unit Price1 or the Quantity1 fields are updated, naturalForms will re-calculate the The Total will be updated every time that either subtotals, paid amount, or tax changes in naturalForms.

Here is what your rule should look like:

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