When you click inside of a pivot table, it's area lights up with a blue
border and the pivot table menu pops up. How does it know this? Is it
a control (like an embedded option button or combobox), or ... i'm not
sure what else there is.

Regardless, suppose I want the same thing in one of my XL apps. I would
like to have the spreadsheet know when I enter a special region,
changing the context menus, showing/hiding custom floating controlbars,
etc. However, I would like it to be general enough such that it is not
tied to any particular workbook (meaning, I assume, it must be in an XLA
or COM addin). And although I have an idea how to implement this, I
would like to know if anyone else has tried this, and if so, what
problems they encountered.

I assume that I would be able to do all of the contextual stuff just by
keeping a log of what the special regions are and trapping the selection
change event, but I have absolutely no idea to implement something like
the PivotTable's ability to display the text "Drop Data Items Here" on
top of the spreadsheet when active or handle problems like the user
inserting rows above the special region, thereby changing its address,
or the the pivot table denying the user the ability to delete rows
inside of it ("You canno change, move a part of, or insert cells in a
PivotTable report...").

Any help would be greatly appreciated.