I've been experimenting with using the parameter property of custom controls
to hold the knowledge of what context the control should be enabled or not.
This is based on ideas from " the Professional Excel Dev" book.

I'd like to incorporate this into a 'generic' application framework that is
reusable across projects, and it would help a lot to apply the concept to
custom command bars as well. I see there is in fact a Context property, but
I can't find much anywhere about it other than the implication that it is
meant for storing the bar's location. I don't want to use this if it is
going to have unwelcome side-effects somehow, plus I'm wondering why the
authors of the book didn't use this property (suspecting there is a reason
why not).

Thoughts much appreciated...