Problem looking lost packets

Hi!
I'm working in a program that sends video files from a machine to another 
one. I would like to know how i can know how many packets have been lost and 
the fraction lost. I've seen that it's possible looking ReceiverInfo, but my 
problem is that i only can receive RTCP packets from Sender to Receiver, and 
those are SR Packets and I think that the packets I need are RR packets.
Somebody knows how can i do it? I wanna do a flow control looking the 
packets lost and reducing the rate if that value is higher than a maximun.
The program i use is based on demo programs (RTPSend and RTPListen).
The way i've seen that no RTCP packets arrive at Sender is redefining 
OnGot(SR-RR-SDES-APP-BYE) functions like is done in RTPListen.
Thanks