Prompt when you Open
If a previously "installed" add-in is moved or deleted, the next time you close and re-open Excel you will see the following prompt.
If an add-in was ticked and then becomes unavailable you will see the following prompt when you open Excel.
This prompt displays the folder path and the filename of the add-in that cannot be found.
This message will appear every time you open Excel until you remove this add-in from your list.
Prompt when you Select
If an add-in that was not ticked becomes unavailable there is no prompt when you open Excel.
The only time you will see a prompt is if you click on this entry in the Add-ins dialog box.
Selecting it in the list will display the following prompt.
Pressing Yes will remove the add-in from the Add-ins dialog box list and remove the corresponding registry entry.