I am trying To USB Function as Usb Host Client Driver, Is It OK

Hi Experts,
I am working with Armbased board with Intel PAX270 processor and WinCE50.
My BSP Supports both USB functioin and USB Host drivers.I am tring to load
Usb Serial Function driver for my USB to Serial device(my Modem).

I wanted to load USBFNSER driver(usbserialfn.dll) when I plug in my Device.
How to load that driver for my Devcie. I need help on Registry settings.
I want to the load the usbserialfn.dll driver using my device VID and PID
Group info.
I don't want to use any Class OR Interface Group.

My question(s) is:
1) is it possible to load usbserialfn.dll driver to my USB to Serial Device?
2) What are the registry settings for loading this driver to my device with
PID VID information?
Your valuable suggestions are always appreciable.
Thanking you all.