Sounds like we're doing some slightly different things.

My Add-In doesn't put in any new menus, just some subroutines and functions
for database access to an Oracle database.

There is a connection to the database in there, which we want to have
available when a given workbook is open, and not available when that given
workbook is not open.

You wrote:

"You are trying to close XL but you are saying do not close the addin."

It's actually sort of the opposite of that. Whether or not I'm closing
Excel, isn't the question... just the workbook. If the workbook closes,
uninstall the Add-In. If the workbook opens, install the Add-In.... is what
is wanted (partially by management).