[ns] automated generation of traffic - please help

[eem2dh]

I am currently doing a project where I have to simulate a channel with limited capacity. I have to simulate a scenario were a fixed number of users generate traffic in a dynamic manner (based on some statistics). Therefore I do no want to use static "at" events  but rather an automated traffic generator that will initiate traffic flows on its own.
 
Is there anyway this can be achieved?