Can't you loop just once?
regardless of the first condition (space bar pressed) loop trought all the lasers and perform collision detection.
then loop through all the lasers again, but this time check if any of the have hit anything or are off the screen. If either is the case, delete this laser, then reset the counter(the goto) and go through the loop again, checking for obsolete lasers. I've noticed that this is *rather* memory intensive tho! I need to find a new way, but for the moment, this is what i'm doing.