script to change widows update permissions

I want to allow windows update when ordinary users are logged on, I'm pretty sure that adjusting the permissions registry entry HEY_LOCAL_MACHINE/SOFTWARE/Microsoft/Windows/CurrentVersion/WindowsUpdate to allow acces to all domins users does the trick.

I already have a logon.bat that runs at login to map drives, etc - what do I need to add to automatically change these permissions?

Thanks