The reason i need this feature is when people wants to make "hacks" for scripts. Then they often modify the scripts a bit, and add lines everywhere in the script. If you then distribute the hack, you need to tell them where in the script they add the lines. The problem is they already have other hacks installed, so it doesn't look the same. So i thought of a trigger_line() function. load the function with a parameter of filename, line number and function to run, then when it reaches that file/line it runs the function, to do what it needs to do. Then it's easy to have a bunch of hacks to a script, without modifying the code. This would be very very usefull.