This is a somewhat offbeat take on the problem, but it might just be of some value. I used a shell extension called FileTip from PC Mag some time back.
<hr>FileTip is an extension to Windows Explorer that displays information tooltips when you place the mouse cursor over a filename in an active window. Microsoft Office provides a similar feature for Word, Excel and PowerPoint files. To distinguish tooltips created by FileTip from other tooltips, FileTip prefixes the tooltip text with the heading "FileTip:". A configuration utility lets you add extensions to different file types. Also, the utility's open architecture enables developers to add new FileTip Extension DLLs without changing FileTip itself. <hr>The point being that the C++ source code is supplied and it may just be possible to find how the docprop information is gleaned, and use that method for your own purposes. Just <img src=/S/2cents.gif border=0 alt=2cents width=15 height=15> worth of alternative possibility.