You can forward RDP traffic at the network level as many times as you like, but once RDP connects to a workstation, the connection has found its point of termination. I suppose an application could be written to listen for RDP traffic and then forward it to another device, but given the fact you can do this with regular port-forwarding it seems unlikely to exist.
The option at your disposal is to connect to the first computer, then from it, connect to the second. You could also configure the second computer to accept its own RDP traffic (listening on a different port if necessary).