this is a tricky one .please help

i have two pcs , one is connected to a netgear router through one of the ports , my other pc ha a wirekess card - so i have set up a kind of wireless network- here is my problem - i have one of those three usb broadband dongles which attahes to a pc via usb -- but i want to config the littel setup so both can use the internet at same time , so sharing the connection - i have tried alsorts and it has sent me crazy - there must be a way to have it connected to the pc which i use as a kind of sever and enable a share so that when net is on on that oc i can also use the net on the other pc-
PLEASE HELP THIS DRIVING ME CRAZY

MANY THANKS SPENCER