Help key

[Beat Cornaz]

Is the 'help' key (on mac keyboards) a good idea?

I am looking for a good key to invoke a special help function. If the  
user presses this key, then visual feedback by means of an image of a  
question mark will be displayed if the cursor is within an object  
that has this special help function. By clicking, the user will be  
taken to that special help part.
I have considered the 'h' key, but it interferes with fields, meaning  
if the focus is on a field, it will write 'hhhhhhhhh' to the field.
Function keys leave also a trace in a field (the square for  
unprintable chars). The control or command keys are being used for  
other things.
The 'help' key (keyNr 268762986) can be trapped and does not do  
anything in a field, so it looks promising. I noticed that in other  
apps, if pressed, it shows a question mark, but not in my stack. (I  
can code for the question mark and all other stuff I need).

I guess my question is : Does this key also exist on all Windows  
keyboards (or is there an equivalent) AND can I safely use the 'help'  
key in my app, so it does not interfere with anything that is there  
anyway. And will this work on all systems (I am on Mac), like XP,  
Vista, Windows 7 etc.

If the 'help' key is not universal, would the Escape key be a  
solution? Or any other suggestions?

Thanks a lot,

Beat