Form Variables and Calculations can be used to evaluate mathematic equations and functions. The results of these operations can be stored and referenced in your rules. Traditionally, calculations would require the use of script in a Calculation field, but many common functions can now be performed using Form Variables.
To setup a Variable, click the Rules button. You will be presented with the following screen:
Click the Calculations/Variables tab, then click the Add Variable button as shown below:
Select the Function you are wanting to perform. Depending on the function you chose, you will be presented with different parameters or options to configure. For example, with mathematic functions, you will be asked to select from a list of Numeric fields you want to add together and for Date/Time operations, you will be asked to select from a list of Date/Time fields.
Naming Your Variable
It's important to name your variables with logical names as these will be what is used in your rules and other areas of your form. For example, if you are calculating a persons age in 20 years, a good name for the variable would be Age In 20 Years.
Using the Variable List Filter
When your form grows in the number of variables, a filter or search utility is available to find all Variables that reference a particular field. Simply type in a field name in the Filter search box and your list of variables will be narrowed to Variables that are linked to that field.