I know it is possible to add your own scripts but it's a long time since i tried. To be honest I've found it easier to work using USMT. It is more complicated but is far more comprehensive and probably the way to go in the future rather than with the built in PM especially if you want to go beyond the built-in functionality.
Mark Star - MarXtar LANDesk Enhancements
Home of Power State Notifier & Wake-On-WAN for LANDesk