Interactive Buttons - Open File - How do I open a file in a "new" window?

Running CS5 and I'm working on an interactive document.  I have created a Button and my Action is to "Open File" and I've selected the applicable file.  When I export to PDF and click on that button, it opens the file but not in a new window so I lose my original source PDF.

I know that I can do these actions in Acrobat but I'd prefer to do all my actions in InDesign so I don't have to keep going back and forth.

Thanks!!