It seems as if the add-in is not loaded if I open the document by
clicking
on it in the windows explorer.

I don't have your add-in of course, but if I select an add-in from Tools,
Add-ins such as the Analysis Toolpak or a custom one of my own, it does
load
when Excel is closed and I double-click a file. That's not true for you?

No.
If I open the workbook by clicking it in explorer or something like that,
the add-in will still be checked in the add-ins menu, but the 2 buttons that
should be on the toolbar are missing, and the function that would retrieve
the data causes the errors I mentioned in my earlier post.


Kind regards,
Bruno van Dooren MVP - VC++

http://msmvps/com/blogs/vanDooren