Problem with hardcoded numbers and letters in a Flex 3 replace statement

Question

Hi,

I've got the following Flex 3 lines, that I need some help with. I'm using javascript with Flex and I need to reformat somethings in order for it to work.

myReturn = myReturn.replace( 'width=468', 'width="468"');
myReturn = myReturn.replace( '&contenttype=png', '&contenttype=png' );

The problem is that I've hard-coded the width at 468, but the width could be any number. And the contenttype could be something other than a png-- a jpg, tif, or gif, for example.

Basically, I want to reformat myReturn as above, but without the hardcoded 468 and png. Is there a Regex that could solve this problem? Any other ideas?

Thank you!

-Laxmidi