Sam,
The simplest way manually is to delete or move the file that the add-in in
the list is pointing to while Excel is not running. Next time you try and
load the add-in Excel will say it can't find it and prompt to remove from
the list.
If it is in your add-ins folder move it out.
The more complex way is to look in the registry under the following keys
HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Excel\Options
where you will need to rename the OPENn keys if you remove one with another
above it so that they remain contiguous.
and
HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Excel\Add-in Manager
where I think you can just delete them.
To do it in code is tough since you need to access the registry directly and
deal with renaming the OPENn values.
Robin Hammond
www.enhanceddatasystems.com
Check out our XspandXL add-in