Ordered printing of random file types in VB.Net

[baffled]

Here's the setup:
- Windows Forms app that needs to print a set of files in a specific order
- Files will mostly be Word docs and PDF docs, but could also be TIF, Excel,
etc...
- The files need to come out of the printer in the order that they are sent
to the printer (Word, Word, pdf, pdf, pdf, Word, pdf, Word, etc...) because
there are a lot of them and we don't want users to collate them.
- We don't want the user to have to do anything other than click a button
that says "Print". Although, if they could initially choose a printer (as
opposed to the default printer), that would be great.

Any ideas on how this might be accomplished? I've tried using various
implementations of the Process class, but in every case, all the Word docs
come out of the printer first, then the pdf files.

Thanks in advance!