In halo 3 you can rig the spawn max on an item to be less then the amount of items that are supposed to be on the field. For example, fusion coil A1 spawns at the start but has a 45 second respawn and fusion coil B2 doesn't spawn at the start but has a 30 second respawn. If you set the max spawn to 1 than destroy A1 than B2 will spawn. B2 won't spawn unless A1 is destroyed and A1 won't spawn again unless B2 is destroyed. Sadly in Halo Reach this doesn't work ><, the object max always jumps back to the amount of objects on map +1. I was really looking forward to having that be a way to let people plant their own trip mines by having a trip mine in a useless spot be destroyed than another would auto spawn in the main path. And no, you can't rig spawn sequence to work it either. Which makes me wonder why did Bungie put spawn sequence on all items to began with? If anyone doesn't understand wth I am talking about go to Rusty Eagle's Forging 101 post on switchs and read about the Instance Switch http://www.forgehub.com/forum/forging-101/7506-switches.html