Customization of Forms toolbox

My project consists of an Excel COM add-in that was developed using
Visual Basic.

The COM add-in inserts a toolbar to Ms Excel upon start up. The
toolbar contains buttons that allows users to access the different add-
in functionalities.

Now I would like to add more functionalities to this application:
The toolbar would be enhanced by adding new controls to the toolbar
that would mimmick controls in the Excel Forms toolbar.
For example, I would have a combo box control in the toolbar that user
could select, and then drag or paste in the Excel spreadsheet. User
could repeat the operation so multiple combo boxes would be created in
the spreadsheet.
Once pasted in the spreadsheet, the combo-box controls would be
populated with entries from the com-addin source code. Furthermore,
all combo-box events would have to be relayed to the Com-addin so it
can be fully managed by the dll.

All the research I've done on this topic seems to point towards combo
box that are active in the toolbar itself, but not on combo control
that are active once pasted in the spreadsheet.

Is this possible?

Any help or leads appreciated.

Thanks.

Guillaume