Notes/Domino 4 and 5 Forum

I'm sure this is a simple question, but I have searched the forums and cant find the answer.
All I want to be able to do is check that when a response document is created, there is a parent selected and not another response.
The response form is setup as a response type, but it still allows me to create it even if a response is selected rather than a parent, which means that certain fields are not inherited.

David