Vista - adding context menu items thru regedit

There's a stellar walk-thru here that shows how to add a context menu item in the registry. I need to go beyond that.

I'd like to open a folder in a program from the rt-click menu. So I followed your instructions to build the entry & it shows up nicely now in the context menu. But clicking that program only opens the program, it doesn't "add" that folder to the program.

For example, I have rt-click menus for adding a folder to WinZip which act specifically on that folder. I need to build the same type key for another program. Following the examples I see from other programs it looks like some combo of %add/ or such. I'm going to play with that for now.