In the Rules section of the Designer, rules can be created to validate field values with patterns, conditionally control whether or not a field is mandatory, and to calculate the value of a field based on changes to other field values. The four kinds of rules that you can set up for a field are:
Pattern Match - Pattern match validation rules work by testing the field's value with a regular expression pattern.
Conditional Mandatory - Conditional mandatory rules work by setting the field's mandatory property to the expression result (either true or false) whenever a value used within the expression changes.
Sum of Field Values - Sum of field values rules work by setting the field value to the sum of values from a set of other fields whenever any of those values change.
Simple Expression - Simple expression rules work by setting the field value to the expression result whenever a value used in the expression changes.