Actually, your idea sounds exactly like an OBJ map I've been playing on a lot these last few days, called Great Escape 1.4. Allie POWs at some Stalag or other have to escape, either through a tunnel or by blowing up two successive gates. Maybe that's actually a beta of your map? :-? If not, you should probably check it out so you don't end up doing something too similar. (got it off
http://www.lol-clan.net)