Send Messages to Known IP addresses

I am ISP ( similar to AOL). Users IPaddress are assigned by our server when they dial to get internet. I like to send messages ( a web page) whil they loged on. I know their IP addresses from my Radius. I dont want them to download any program. Cookies may be ok but if this can be done without cookies that is preferable. This is done windows envoironment. IIS server, .net is available, asp or asp.net 9php will be considered if that is cheaper than other solutions) Thanks ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform windows 2000 IIS .NET asp or asp.net c# or vb 6 will listen to suggestions