Hello.  I'm having an issue when I Override the New button a custom object.  I'm unable to get a value from the merge field or a specific object type.

I want to Override the New button for custom object X.  X has a master/detail relationship to Account, and a lookup relationship to Y.  I want to be able to go to the detail screen of a Y record, click New on the X related list, and I want to be able to access the Id of Y. 

However I don't seem to be able to get Y.Id.  I can get the Account Id (if I am on the Account detail page).  Is this because Y is a Lookup relationship and not a Master/Detail relationship?  Do I have to do this as a standard scontrol instead of as a New Button override?

Thanks for your time.
Chris