Struggling with something seeming really simple

Hi,
I want to to do a condition in my TCL script to check if the incoming traffic rate is higher than the link bandwidth in order to detect a possible congestion. I don't know how to that condition line. Can anybody help?
OR alternatively:
making a condition in TCL script in witch i have to verify if the number of packets in a link queue has reached a certain threshold so i can prevent a possible congestion in that link. Can someone provide me with the code for that? Thanks.Either way my goal is just to implement a simple solution to detect congestion.
Thanks in advance smile emoticon