Back Button works one way for execute and another for enter

I created a custom program that includes a selection screen and a detailed list/table output. When a user enters their selection criteria and hits enter (instead of execute) they'll go to the next screen, and when they are ready to back out, it goes back to the selection screen, which is correct. But when a users enters their selection criteria and hits the Execute button, they'll go to the detailed screen and when they press the back button, it backs out of the program completely. I don't understand why their is a difference between the two and how it would affect the back button. Also, I don't know how to get the execute button and the enter key to act the same way. Can any one offer any suggestions?