Networking

We have a wireless router in the office… the only problem is that all the computers can read each other and the link between me and my partners computer is no good…

If i use a router to connect our two computers is there a way to network out two computers through the hardware router but keep the internet connection that we currently use (the wireless one)?

So can i have a CAT5 connection between our two computers and have them be able to share files… while at the same time taking the internet connection from the wireless router… any help would be greatly apprecitated