For my test , i use the software Franson GpsGate that simulate a GPS signal on a virtual com port .
You can to define several com port and use each com port for one sofware (it's a splitter of com port ).
But you need to create your own itinery (.gpssim file) .
I use Itnconv 1.78 for create my itinery , i save this itinery as a .kml file and convert it in a .gpssim file with the gpsbabel converter !
I have made an autoit script that does all these steps quickly : ItnConv2GpsGate
I don't know if that will help you !