I have a form with a subform. Both forms are connected to individual tables. The main form has two fields: custname and custid. The subform has a relationship to the main form based on custid. The subform has two other fields: chargedesc and charge (currency). Basically the purpose is to enter a customer into the db and put in all the charges for the customer by charge type. What I would like to do is put a third field into the main form that would calculate the total charges based on the sum of the charges in the subform for the customer currently being viewed. This field should automatically display the total on the form. What is the best way to do this?