Edit receive Functionaility in USRP Echotimer for USRP Source

Hi,
I am using USRP Echotimer block that has one antenna as transmitter and other (RX2) as radar receiver.
In my design, I want to switch between radar receiver to normal data receiver. The gnuradio does not allow to use an USRP Source as a block within the same flow graph as of USRP Echotimer.
Is there a way to change the source code of echotimer to add the functionality of usrp source, or is there an obvious way to do this that I am missing.

Thanks,
Abhishek