Need help with maths

programming flash
1 
knob_mc.addEventListener(MouseEvent.MOUSE_DOWN,turn);
stage.addEventListener(MouseEvent.MOUSE_UP,endTurn );

function turn(e:Event):void
{
    stage.addEventListener(MouseEvent.MOUSE_MOVE,turn);
    var position:Number = Math.atan2(mouseY - knob_mc.y,mouseX - knob_mc.x);
    trace(position);
    var angle: Number=(position/Math.PI) *180;
    trace(angle);
    knob_mc.rotation = angle;
}

function endTurn(e:MouseEvent):void
{
    knob_mc.removeEventListener(MouseEvent.MOUSE_DOWN, turn);
    stage.removeEventListener(MouseEvent.MOUSE_MOVE,turn);
    knob_mc.addEventListener(MouseEvent.MOUSE_DOWN,turn);
}

This is the code I’m using to move a knob the challenge is when i click on the knob it turns 90 either left or right depending where i click, I’d like it to stay still until I turn the knob, and second how do I get the angle in whole numbers??