I've seen one here 
http://hermes.ceb.ucop.edu/CEBOnline/olprograms/olphow.html
click the 'Install/Use the RealPlayer' link to see it in action.
Maybe they'll tell you how it works if you ask them nicely :-)

HTH
Phil
>---------------------------------------
> Anyone have a script that works in both IE and NS and on PC and Mac that 
will detect what version of realplayer a client machine has installed?  
Any 
help is appreciated.  Thanks!

t3kn0