I'm not sure what you are trying to do. Are you simply trying to change the alto clef to a G or F clef for the keyboardist? If so, I would suggest you add a staff with the appropriate clef and copy the viola part to it. Use the added staff to generate the keyboard part and then hide the added clef in your full score.

(Does F 2010 have staff styles that you could use to hide the added staff and collapse the score? You could also create a part containing all staves except the added one and use that as your conductor score instead of the full working score.)

That is a very good solution.  If the viola part is copied to a separate staff in bass clef in the score and then hidden, that makes it possible to generate the part I need for a keyboardist.

Thanks for the suggestion.

If the clef changes happen at barlines, then there is a simpler solution:

Staff styles can be different between score and parts.

Create a custom staff style that does not do anything but set the clef.