I think the best way to do it (it's been discussed in varioous threads in this forum) is to have Centrex lines and have the VM do a Centrex transfer to the cell phone.

I'm not sure, but I don't think the DSUII can do a trk to trk transfer---I'm sure a regular Comdial mod will add something concerning that.

Just recently, someone responded to the same type of question and had an answer---but right now, I don't recall what it was. If I find the thread, I'll let you know.