How to make a computed field?

A computed field is a field that do not require the user to enter a value, it is computed with other fields values.

The computation rule is a short Javascript code. Other field values can be accessed with the following syntax:

$('VARIABLE')

where VARIABLE is the name of the field from which the value is to retrieved. When the field is in a group, use a . for building the full name of the field. For instance, if the field with name VARIABLE is in a group with name GROUP, the value of the field will be:

$('GROUP.VARIABLE')

Examples

The computed value is the sum of other numeric values:

$('VAR1') + $('VAR2')