Help with speed control set up

[zombieslayer16]

We are using a sonar sensor with our robot, we want the the robot to slow to a stop when in a certain range of the wall. That range is defined at the average of the minimum and maximum values defined by the driver station. I know we could implement a more elegant solution but with our limited programming skill this is the best we could come up with. The problem is that when the button is held down the robot seems to constantly go at a slow speed and never slows to a stop, even when started at the stopping point and the button is held.

Thanks in advanced