Hide a UserForm on workbook deactivation

[aca]

I often have several workbooks open and shift from one to another.
One of these contains a floating UserForm; and the trouble is that when I leave this workbook and shift to another one, the UserForm belonging to the first remains open and visible in the new workbook; and I cannot hide this nuisance.
Within the same workbook, it’s easy to hide the Useform when shifting to another worksheet (through code for Private Sub Worksheet_Deactivate()).
Is there something similar for when the whole workbook is deactivated?

Thanks for any help.
ACA