Extending serial ports

dear all,

i wanted to increase the number of serial ports, by using USB port in 
my board, how can we do that any 1 has idea?

well i will use a usb to serial convertyer device, but for that i 
will require driver rite?

so where can i get that?

well in desktop windows that converter is automatically detected, OS 
assigns a COM port Number also automatically, but to activate it in 
win CE what will i have to do?  or which COM port it will take it as?

any suggestions will be greatly appreciated.

thanx


Nirav Kothari