A script handler you can implement to override standard MoneyWorks behaviour.
Automatically called: When a field becomes active by being tabbed into or clicked.
Use for: Preflighting a field (maybe to save the contents before the user changes them).
Return value: ignored
Specific Naming: You can and should implement an EnterField handler that is specific to the particular window ID and itemID of interest. e.g. EnterField:<WindowId>:ItemID:<TransactionType> (the last of these applies only when the WindowID is F_TRANS)