слоупочно конечно, но на всякий случай
Код AS3:
var minScale:Number = 0.01;
var maxScale:Number = 10;
object.scaleX = Math.min(maxScale, Math.max(minScale, object.scaleX + mouse.delta / 150));
Код:
scale = object.scaleX + mouse.delta / 150;
if(scale > maxScale) scale = maxScale;
else if(scale < minScale) scale = minScale;
object.scaleX = scale;