How do u cancel out the lorentz force which causes the electrons to move in a circular motion wen charged in a?

You mean, say, the electrons are moving horizontally through a magnetic field that is horizontal and perpendicular to the electrons' motion, and you want them to keep moving horizontally? Just make qvB = mg. Since you can't change q or m or g, change v or B.

we may be talking at cross purposes here..the L-force for a cp is

F=Bqv in magnitude..this will make ur electron travel in a circle..rad r=mv/qB..if u apply an E-field at rt angles to B such that E=Bv..then electron travels undeflected

alt if ur talking abt electron travelling in grav field and mag field..then it has helix or cycloid path with drift vel=v=mg/qB..to reverse this drift u need an E-Field equal an opposite..mag E=mg/q