So, it sounds like you want to use a 3G dongle as your source for the internet, and you want to create a network so the 2 computers can share the one dongle.
You will need a WiFi router to accomplish this. While not all routers do this, certain ones that have USB ports will allow you to insert a USB dongle into the port, and will use this as an internet source. Asus routers are known to support this. I've pasted a link to their routers in various countries that will do this.
http://www.asus.com/event/networks_3G4G_support/