Yes, u can use old and new qualifier only for database row trigger only.
As far as i know there is no way to use : old and : new in forms....
Rather you can do something like this
Take a cursor of the table matching the last saved record
This will do what you want...
I think the closest thing you will find to the :OLD/:NEW operators in Forms is the Get_Item_Property('ITEM_NAME',DATABASE_VALUE) built-in. You can compare the value returned by this built-in to the current value of the item to see if the value has changed since it was originally queried into the form. This will only work, however, if Forms queried the value. If you manually fetch and display a value, then this built-in will return NULL.