How do you link a workbook to an add-in? Here's what I'd like to do.

After opening a new workbook, a user can select an add-in (from tools/add-ins). This would
a) do some initializations and b) link this particular workbook with the add-in. When reopening the same workbook, the add in would still be available. This would of course apply to any number of workbooks where the procedure is followed.

On the other hand, if on another workbook the add-in wasn't selected, all the initializations, etc. wouldn't take place.

Thanks

Julio