Bitmap to Vector on the fly? (or another scaling solution)

Hey smart people!

Here is my problem. All of my artwork is done in vector graphics except for some images that I load off the disk at runtime which are in .PNG format. My flash application runs in full screen, and due to vector graphics scaling nicely, everything looks very smooth, except for the PNGs. The PNGs look very blurry and ugly.

I would like for the PNGs to look nice like everything else, so I was hoping there is some way to convert them to Vector Graphics on the fly using AS3. Unfortunately, importing them into the Flash IDE and using TraceBitmap is not an option because I use the bitmapData from the PNGs later to divide the PNGs into little square pieces. At that point, my nice vector from the FLA turns into an ugly bitmap.

So is there any way to convert my bitmapData into vector graphics on the fly so they scale nicely? Or does anyone see another solution to this problem?

Many thanks!