How to assign default AutoPlay handler?

Hi Group:

I want to assign a program as default AutoPlay handler
through changing registry values, and I find the key is
"UserChosenExecuteHandlers" in
\Software\Microsoft\Windows\CurrentVersion\Explorer\Autopl
ayHandlers under somewhere in HKEY_USERS; the value of
the key seems also machine dependent.

The question is how to set it correctly, I cannot find
useful information on MSDN, can anyone help me?

Thanks :-)