In an add-in I have created, a custom menu item is created, it is
disabled at the end of the macro that created it with:

CommandBars(1).Controls("blah blah").Enabled = False

I did this because not all workbooks should be able to use it.  The
menu is created and greyed out when Excel is started.

In the workbook_open macro of theworkbooks I want the menu to be
available, I placed:

CommandBars(1).Controls("blah blah").Enabled = True

to turn it back on.  When the workbook opens, I get:

"Object variable or with block not set"

I haven't been able to figure it out.  Any help would be appreciated.