Is there a way to provide mouse/kbd input from one computer into another computer via USB cable
Solution 1:
How about a KVM without the "V". A KVM simply switches the keyboard, video (not in your case) and mouse. Many KVMs can be switched with a hotkey such as <shift><shift>.
Here is one possible product: http://www.newegg.com/Product/Product.aspx?Item=N82E16817107417
Solution 2:
what about a virtual network combined with synergy? Programs like Hamachi can make multiple networks act as one virtual network