(SOS) Extrude Polyline According To Closest Points

Hey Guys,
I have a surface, which i subdivided in certain no. or polyline plots.. I have 3 reference points (eg. A, B, C). I find which Plot centre points is close to A, B, and C.. Now I want to extrude the polylines and i am not able to understand how do i link this (closest point) data while extruding.. I was able to extrude it according to the distances from A, B, C to plot centre points, but i want to extrude the points closer to A by say 5 metres, closer to B by 10 and closer to C by 15..

Can any one help me out with this..

Thank you