Hi rberger,
There is no simple setting that will allow you to dedicate the ENTER button to open the menu. However, with a little bit of magic (Event Structure looking for ENTER key press), you can programmatically (using the "keybd_event" function in "User32.dll") click the ALT (Menu) key and then the ENTER key. This combination will always open the menu list (try it manually first; ALT and then ENTER).
Try the attached VI that I created for you.
Have fun!
- Philip Courtois, Thinkbot Solutions