Forcing i530 to strongest tower

Hey all,

I'm in a border town ... when I cross back and forth, my phone keeps jumping from a telus mike tower to nextel .. .the nextel tower is strong, the telus is weak where I am, and I lose signal.

Is there anyway to force the phone to chose the strongest tower instead of taking the first wimpy telus / mike tower signal over a strong nextel signal?

Thanks!
Col.Wild