Editing Wondercards

Not sure if this is the right place, but whatever. Correct me if I'm wrong, please.

I'm at Tekkoshocon IX in Pittsburgh this weekend, and I got an idea to make a custom event Wonder card for Black and White (or at least one for any of the five gen4 games) since I keep meeting a bunch of awesome Pokebros, and wanted to give some 'mons out instead of just trading version exclusives to people that need them for entry data sake.

My question is this: How do I go about doing this, if it's possible.

As it stands now, I have distro ROMs for several of the D/P/Pt wireless events, and the 2011 HG/SS Johto beast/Celebi Gamestop ROM.

I'm not sure if it's possible yet for Black and White, but I know you can do it with D/P/Pl/HG/SS using some programs.

Here's a guide on how to do it.