Reviews: I don't know how to solve you problem, or if it is solvable with the equipment you have, but do a Google search on the terms "Airport", "NB5Plus4W" and "WDS" and see what comes up...I guess other options are to buy a wireless card that will work in the G4, or perhaps one of those USB wireless thingamebobs (do they work...
Retrevo's Recommendation: Average Buy for Everyone