I didn't notice that anyone had posted replies; thanks. I looked further into this, and finally kicked VS2005 around enough to get it working. As Dusty said, it was a combination of registry key and usertype.dat. The steps are as follows:
1. Add a registry key:
Key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\8.0\Languages\File Extensions\.wdl
Value: "{B2F072B0-ABC1-11D0-9D62-00C04FD9DFD9}"
2. Add a blank text file called usertype.dat to "C:\Program Files\Microsoft Visual Studio 8\Common7\IDE".
3. Populate usertype.dat with the latest C-Script keywords (one per line):
Quote:
function
starter
action
var
(etc.)
4. Profit!
YMMV. Use at your own risk. :)