I would like some further information, but to begin here are some pointers:
If your problem only lies when users add a new record, you can use the form's
BeforeInsert
orAfterInsert
event. These events are triggered as soon as the first character is entered in a field. (Access automatically inserts a new record)You can use those events to pre-fill some of your textfields if that is the case.
Similarly, when the record changes are saved (for the complete record, all the fields, indicated by the little pencil on the left of the record turning into the arrow), the form's
AfterUpdate
event is triggered. You can use this event to update one value or another.
I think these 2 cases will cover your needs. If not, please supply some further information as to what exactly the changes you want, are.
Hope I helped. :)