ASP.NEt Download Buffer

Does anyone know how to create a download buffer? I'll explain a little bit. What I mean by a download buffer is a script that will count how many people are downloading a certain file, then after say 50 or so are downloading that file, it will make everyone else who wants to download it have to wait a certain amount of time(ex. 5 minutes).

I got the idea from Fileplanet.com and Fileshack.com. Seems like a pretty cool system and it appears to be written in asp.net on their sites.

So if anyone knows how this could be done, please reply.

Thanks
Rev