Greenhouse Inventory & Invoice App.

I have an inventory and invoice program for our plant nursery/greenhouse operation. It is written in VB6 calling an Access 2000 db. I want it to utilize a MySQL db instead. Additionally, I want to add a component/module to allow for tracking client balances and payments, thus an Accounts Receivable component. I want for cust. balance to show on Invoice and Order screens, preferably in red if they have an outstanding balance owed and black if Zero or a credit. That's it!