Application port when using IESM USB on Fastrack Supreme

I have an OpenAT application loaded and activated via the serial port.
This application communicates back via the serial port. All this works fine !

I then insert the IESM USB module, and enable the module with AT+WMFM=0,1,3
I then Open a Hyperterm connection on the new COM port, and I can get the AT prompt OK.
But now my application does not respond.

I assmue its does its read/write on a different port? (still the standard serial)?

Question: Is it a command to make the application port the same for serial and the USB created COM port?

The reason I need this, is that my customers sometimes order a serial only device, and sometimes the USB configured,
and I would make my application config as simple as possible, and work without modifications on both ports.

Thank you for any support on this !