Scaling an object porportionately to its y position trouble

I’ve got a slight problem with a flash file I’m doing for a neighbour… She wants different draggable objects on the screen… That is fine, but she also wants them to scale themselves too. I’ve got the scaling working by calling this function inside every inside every onPress.

function scalePicture() {

This does almost what i want except it doesn’t keep an objects proportion in comparison to another object. If I have one movieClip at 150 px in width and another at 50px in width they both end up the same size when at the same height.

I understand as much that I need to somehow tell the scalePicture funtion that this objct is slightly bigger but cant figure out how. Any hints would be greatly appretiated.