Ray, you're a genious. When I started to write out exactly what I did, I found my error. It was an error in populating the radio buttons. It works perfectly now.
For the record to possibly help others:
I added 2 radio buttons in a group labled rbPrice and populated the values with my monthly price and annual price that are fields in my item table. This is what I put in the Value field of the radio button for Monthly Payment.<%=(WADAecItems.Fields.Item("ItemMoPrice").Value)%>
Next I opened the eCart "Add From Recordset" dialog and under the tab, Binding, I bound Price to my radio button group like this <%=cStr(Request.Form("rbPrice"))%>
Ray, I really appreciate your help. Thanks!