Update Query

I have a form with expiry date. The expiry date is controlled by a payment date, which is in another form. When a payment date is entered, the expiry date should move on a year.

I currently have an update query which controls this, however, i have found that it is not looking at the first, but the second value entered to do the calculation and so on - such as below:


payment date 18/09/04 expiry date -Empty Box-
payment date 18/04/05 expiry date 18/09/05
payment date 26/08/05 expiry date 18/04/06

so the update query is looking at the wrong value. is there a way to alter this, or correct/alter it so that the correct value is always seen?