I'm pretty sure you need to full version of CodeWarrior to do this. I wanted to write some BBEdit plug-ins and tried the same thing. The "learning" edition doesn't support building code fragments, only standalone apps. I'm sure the link you provided talks about how PB doesn't support that, either. FileMaker plug-ins use this same concept.
Fortunately, I live by a college and just graduated, so I went to the computer store there and picked it up for $120 (saved $280). They didn't ID me or anything, so, if possible, you could always try something like that, I guess.
Good luck.
