Gravity forms and user registration

I thought I would ask the WP community first before putting this to GF direct.
I am looking to save a little cash and buy just the basic GF package.

I would like to create a form in which only registered users on my WP site (I was thinking of using Register Plus Redux plugin) can complete the GF form (if that makes sense!).

Does anyone know if this is possible directly from within GF on the basic package or if there is a plugin or code that might address this issue?

Many thank’s in advance!