Plucker is more or less a dead format, occasionally the devs here get interested in adding support for a legacy format because they have books they want to convert to a modern format. It's pretty rare it's the other way around.
If your husband is a programmer maybe you can convince him to contribute to Calibre - there are python scripts which can convert html to plucker format on Plucker's site, it probably wouldn't be too difficult to integrate them into Calibre, but then again the scripts haven't been updated since 2004, so not sure if they'll need modification.
There are other pocketPC reading programs you could try on the PocketPC which should support eReader, PalmDoc, or Microsoft Lit. Odds are you can find one of those programs and get it installed to your handheld.
Microsoft Reader for various versions of Windows Mobile, most likely including yours:
http://www.microsoft.com/reader/downloads/ppc.aspx
Convert to Lit in Calibre to use it with your books.
@Kathybaug, since you want to go the other direction, convert your plucker doc to html using this utility:
https://www.mobileread.com/forums/sho...d.php?p=561774
Then add the html to Calibre and you can convert that to a modern ebook format.