To anyone who may be reading, and to Franz,

After working in the file some more, I have come to a different theory
on the source of my original problem. I have indexed the file as a
table in Access. When a query is open in Access that includes data
from the Excel file, the excel file is locked for saving. My new
theory is that this file locking being done by Access seems also to be
causing the HLOOKUP problem.

When I reported to Franz earlier that doing what he suggested worked,
I suppose that it may have worked because coincidentally the Access
file was closed at that moment and was therefore not locking the XL
file.

- Paul