InfoPath Dev

I trying to execute a CAML Query (using SPQuery) and the fields in my Where clause have spaces in them.  One of the fields has a Display Name of "Form Type".  I have tried "Form Type", "Form_x0020_Type" and "Form%5fx0020%5fType" in my code but my queries do not work.  When I use internal field name the queries work.  The "Form Type" field is not a renamed title field.  I'd prefer to use the Display Name in my query because the it's the same in both my development and production environments.

Is there something obvious that I am missing? Am I being dopey because I'd like to use the Display Name?

Thanks.

 You aren't silly for wanting to do this - but sadly, it just isn't the way the UpdateListItems web method works. I don't think there is any option to switch to using the display name.