It probably depends on the bar code scanner and the driver software that comes with it. I've seen some bar code readers that have a mode where whatever is scanned gets treated as if it were typed on a keyboard on the PC connected to the scanner. In that case, you could have a bar code containing a file name. Someone would have to click on the right button(s) to get an open file dialog to appear. The scanned bar code would supply the file name and the return key that closes the open dialog. I normally use a Mac and it would be trivial to do it there using Apple's Automator. I don't know how to do the equivalent under Windows.
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- Stephen