To answer your original question, I believe it takes a 25kOhm expression pedal, similar to the VPJr. IIRC, with the DL4, it'll allow you to switch between 2 settings on each of the 3 presets on the pedal. You can morph between them with the pedal as well. I'd think it'd be the same as with the M13- mono cable to one jack or the other on the VPJr., the other to the expression pedal jack on the DL4. The VPJr. isn't cheaper than the Line 6 expression pedal though, but it's buuilt much better and will last a lot longer.
i already have an EB Jr., i just didn't want mess anything up... not a fan of the smell of burning. thanks!