Multiple form fields with same name from db

I am creating a form in my vb dll using a recordset from my sql db. There is 2 text boxes with descriptions, then 2 textboxes for data entry, and 1 that is a calculated value based on the 2 data entry fields. I realize now that the textboxes for data entry and the calculated value cannot have the same id/name.

How do I go about creating this form so when the 2 data entry fields are filled in the calculated value is calculated? I had an onchange even firing but when more than 1 set of data entry boxes is available, it doesn't fire.

Thanks,
Dia