How to fix disproportional scaling across multiple images at the same time in InDesign?

In InDesign CS5, you have to directly select an image and scale up or down after clicking the "constrain proportions" chain-link button in order to revert the proportions back to normal. When selecting multiple images at the same time, this trick does not work. To save time, I'd like to fix multiple disproportional images all at once. Could this be done by writing a script? Is there an easier way?

Thanks! -JD