Based on my googling, I don't think this is going to work for files, despite the appearance that &4000 shows files too. I was able to select a zip file too, likely because windows treats those as archive folders, but was not able to select any other type of file.

Here was a good article that was basically the same question as yours. http://stackoverflow.com/questions/28632270/vbscript-file-or-folder-selection