Running Office XP on Windows XP Home Edition

I am successfully creating a custom toolbar 'on the fly' via an Excel
add-in. However, when I click the close button on the active workbook Excel
prompts me to save it, and at this moment my custom toolbar disappears as it
gets deleted by a Workbook_BeforeClose event.

My question is, if a user clicks 'Cancel' when the workbook save prompt
comes up, how can I still retain my custom toolbar ? In other words, my
toolbar should disappear only when Excel application gets closed.

Thanks,
Amit