Emu XL-7 & MP-7 User's Group

Question.
Theres one button on my xx7 that I never use and what disturbs me is 
that I cant imagine how I´d use it if i needed to. Its has the most 
vague explanation for a feature in the user manual, too.
It´s the program button next to quick edit.
 I use cubase to edit sequences (purely for the graphic interface) 
then load the seqences into my xx7 via e-loader to jam with. 
So, if it is ,as i suspect, for program changes do i need this 
feature?
I noticed that the midi out LED lights up when i turn it. But nothing 
changes on my external EMU vintage keys synth!!!

Does anybody use it? How do you use it?
Any suggestions/explainations welcome.
thx
:Paul