I have a problem where I am running a word mail merge document in batch. The
document needs a duplex printer, so I want to dynamically select the printer
without bringing up word myself. Also when the job finishes, I need it to
reset the default printer back to what it was before running this document.

Say for example my default printer is prta, and my duplex printer is prtb

I need to have my mailmerge document use prtb, and then when finished
mailmerging change the default printer back to prta. I'm assuming to get
this job done, the default printer prta needs to be changed to prtb
dynamically, and then dynamically changed back to prta upon completion.