I've done this:
at the top of the script, before the commands are executed, I entered
if (@ContextNode.SysName == 'xxxxxxxxx')
// Enter configuration mode
.... here are the commands that will be executed...
(instead of xxxxxxxxx you insert your SysName)
This ensures, that the commands are executed only on that particular device. If other devices are selected, no script will be executed on them.
It's a pity that a device cannot be pre-selected (or at least I have not found a way to do this).
Is this what you're looking for?