Seamlessly Switch to best Network Connection

I have two wireless routers set up in my home running on different SSIDs. How do i configure the network connections so that it automatically connects to the one with the strongest signal (which depends on where I'm using the laptop)?? When i use the same ssid on both routers it doesn't seem to siwtch to strongest signal. One other bit of info -- one access point is 2.4ghz wireless G the other is a dual band (2.4 and 5ghz) wireless N.

That's the difference between consumer-grade wifi equipment and the premium stuff which costs big bikkies. The latter can seamlessly "roam" when a user moves through an office building with her laptop, always establishing an association between the wireless NIC and the WAP with the currently strongest signal.

What you want is probably impractical unless your wifi NIC drivers export "accessor" functions which would allow your code to poll for or subscribe to events corresponding to significant signal strength changes. Then you'd have to code the solution yourself (unless the NIC manufacturer already provides a utility or sample code), and that would be far from a trivial exercise.