Create mulitple price options for items on flash with xml

I new to working with flash and could use some help. I have been working on a site that will sell art but would like to allow buyers to select different media that are priced differently (Big prints,small prints, etc.). I can select the print option but cannot figure out how to have the price change automatically. I’ve attached the AS3 script and xml file I’ve been testing.

Any help will be appreciated. thanks.