Downshift override?

[ccbarnett]

I've been on a road trip with my family in my wife's minivan - a 2005 Town & Country Limited - which is a bit of a pig, though not terminally wretched (averaging around 24 MPG on the trip, fully loaded with 2 adults and 2 kids in car seats, plus clothes and beach trip paraphernalia, 90-95% highway).

While playing around with the cruise control, I thought that it would be really helpful if I had a switch within easy reach that would override the auto transmission and keep it from downshifting on uphills. I found (predictably) that my MPG improved the longer I was able to keep the revs lower in overdrive, but the only way to accomplish that on uphills with an auto (without a Tiptronic or some similar improvement) is to kill the cruise and let the speed drop on the ascent. In an MT car, I'd just keep it in fifth and downshift only if things start to get ridiculous. I'd like to have the override switch handy, so that I could trip and hold it at the bottom of a hill and release it at the top or before then if the speed drops too much.

Anyone know if this has been discussed at some point?