Simple answer - you can't. VPC for Windows doesn't support USB.

The only exception to this is if the USB device can be shared from the host
in a way that it "looks like" a piece of hardware which VPC emulates. E.g. a
USB memory stick can be used so long as it is shared from the host so that
the guest can access it via standard networking protocols.

Similarly, does your UMTS device create an Internet connection on the host
which can be shared via ICS? If so, then the guest can probably connect to
it...

You can't.