You can specify a formula that will edit (or verify) a field every time the value of the field is changed. For example, you could easily verify that a line item quantity on an invoice is within reasonable limits. Edit/Match formulas can compare fields across several forms.
On the second Field Description screen, there is a field labeled Edit/Match. You can enter a formula into the Edit/Match field that is evaluated every time the field is changed. If your formula returns an empty string, form allows the change. Otherwise, form disallows the change and displays the string your formula returned as an error message.
Form evaluates the Edit/Match formula in a field in the following situations
The operator has entered a new value into the field
Form has recalculated the Copy/Calculate formula on the field as a result of a change to another field
The current form has been cleared as a result of the operator pressing the CLEAR or CANCEL keys
Form has changed the field values to their original values as a result of the operator pressing the UPDATE key while in UPDATE mode
Form has changed the value of this field as the result of a lookup
A user_edit routine has called swrite to change the value of the field