UA and US Elite: Getting Best Seats on US and UA Flights on Same Itin

I dug through several pages looking to see if this had been addressed and couldn't find anything:

I'm a 1K and I'm Chairman's.

I made the mistake of booking a round trip itinerary through Carlson Wagonlit where I fly direct on United TPA --> Chicago and on my return I fly USair back via CLT.

I guess I was dreaming when I though the united leg could be under my UA elite number and the US airways legs could be under my dividends number.

To further complicate things- I already used a regional upgrade to upgrade the tpa-ord leg.

Is there any way I can prevent a horrible seat on my us airways legs back to Tampa without forfeiting my upgrade on the United flight?

Thanks for any help.