Let me tell u when i was looooooong time ago on an FXP board.
They had some kind of system like this for the scan forum. The first post showed how many IP scanned were posted (next to the thread title on the forum) and inside the thread u had a list with all the ips and a box where u entered a number of IPs u wanted to grab. Enter that name and later on, the script will give ya a list of IP's just for you.
This way u will only see your ip's and nobody else will be grabbing your assignated numbers
If another person entered the thread, the total number of ips available will decrease showing something like (40/180). Already chosen IP's wont be able to be DESELECTED for obvious reasons.
hope i could clear something out. If not tell me and ill try to explain again. Sorry for my english.