Thanks nloftofan1, you have saved me the research time and thanks for including the links. Looks like I won't have to use the "burn CD" conversion technique anymore.
But going back to the OP's question, one option for him is to purchase the track on iTunes. While iTunes supports IMPORTING different formats, purchasing tracks from the iTunes Store are all ACC formats. If Sound Forge does not accept an ACC file as an import format, the ACC file will have to be converted to a format that can be used by Sound Forge, such as mp3 or wav.