Panoramic wifi port forwarding not working as expected.

Trying to port forward. And it will let me do it but not in the method im wanting. 

external(1234)  -> Internal Port(4321) (192.168.x.x)  for example  

all my old routers allowed me to set whatever external port i wanted and route it to the appropriate internal port number.  Ive searched everywhere and it it only allows to set external only? Or am i missing something. Really trying hard to keep with cox standard equipment but i have a feeling they may force my hand and get my own router.