applescript help: run script as result of activating another app

okay.. i know it's possible to schedule script to run at any given time by using ical, but is it possible to, say, run a script when, say, i start safari... or any other given app?

the reason i'm asking is i'm using VNC to remote access my MBP, whic is connected to a external monitor.. at home i work on both mbp's screen and the external monitor, so some of my windows are opened in those... but i want to have all windows go to mbp window when i run vnc... is it possible?

also is there a way to, say, when i send myself an email with certain keywords of commands, Mail receives it and detect those keyword so a given script runs? can i do that with automator, somehow? or any other mean?

thanks for any comment!