I am making a database for a school newspaper. We have a "contact" page for every customer who purchases ads. We also have a "transaction" page that lists all of our transactions (checks we receive from them and purchases they make). We have a subform on each of the "contact" pages that shows all the transactions for just that customer. On our table that feeds the subform (titled All Transactions) we have the following fields;

-Transaction ID
-Transaction Date
-Issue
-Transaction Description
-Transaction Amount
-Company Name
-Check #
-Check Date

It is working fine at showing us the info for each customer, but we would like it to show us that customer's balance per issue. There are six issues, and in the Issue field in the transaction table is a pull down menu to pick one of the six issues (they are called "Issue 1" "Issue 2" etc to "Issue 6"). For orders, we are putting a negative amount into the Transaction Amount box, and for payments, a positive. All issues are being shown in the subform. We would like to have six text boxes labeled 1-6 on the contact page that show us the customers balance for each issue. We've tried the expression builder, but none of our expressions would work.

What can we do to get it to show us the customer's balance per issue?

Are we on the right track? We feel we need balance per issue to generate the proper billing statement, billing letter, and an accounts receivable.