Upgrade PivotTable drop-down selection box
 

Thanks in advance for any help!

I'd like to essentially improve upon the PivotTable drop-down selector
for PivotFields. I use Pivots that have so many options to choose
from that you end up having to click the box, unclick 'show all' and
then dig for the items you want. I basically just want to be able to
type in the one I want to choose, or type a portion of it and filter
the available items.

The ideal situation would be to completely override the current
selection box with my own code. That may be impossible or beyond my
ability. If it is possible, please give me a reference or point me in
the right direction with the code.

If that's not possible... I'm looking for design ideas. I haven't yet
come up with a great idea on the implementation that will be easy to
transfer to other people without having to spend much time on training
them to use it. I want this to be applicable to PivotTables across
the board (i.e. a modification to PivotTables in general, not just one
particular spreadsheet).

Thanks again for any help or ideas you can provide.