Smooth Scaling/Repositioning

programming flash
1

I have an mc that i want to scale smoothly, see attached image that explains it…

heres my code


shrinkMap = function (target_MC:MovieClip, target_WDTH:Number, target_HGHT:Number, target_X:Number) {
    target_MC.onEnterFrame = function() {
        if (target_MC._width>target_WDTH) {
            target_MC._width -= target_MC._width/20;
        } else {
            target_MC._width = target_WDTH;
        }
        // 
        if (target_MC._height>target_HGHT) {
            target_MC._height -= target_MC._height/20;
        } else {
            target_MC._height = target_HGHT;
        }
        // 
        if (target_MC._x<target_X) {
            target_MC._x += (target_X-target_MC._x)/5;
        } else {
            target_MC._x = target_X;
        }
        if (target_MC._width == target_WDTH && target_MC._height == target_HGHT && target_MC._x == target_X) {
            delete target_MC.onEnterFrame;
        }
        // 
    };
};

It looks really jerky, the different bits finish before each other…is there a way of making each bit (height width and x) scale in proportion of each other so they all finish at the same time? I bet its something to do with what i divide the -= values by (currently arbitrary numbers like 20 or 5)