"As you were" sounds stupid enough with drill commands.
If you change your mind in the middle of answering, just say, "correction, ..."
For example:
SGM: "What regulation covers the wear and appearance of the uniform?"
SM: "AR 600 dash...correction, AR 670-1, SGM."
I am by no means a board genius, but I've won:
- BTRY SOQ
- BN SOQ
- BDE SOQ
-

2nd place, Corps SOQ
- CJTF-76 NCO QTR
- CJTF-76 NCO YR
I also trained two soldiers, one made it to Post SOQ and the other won CJTF-76 SOY.
I've always used that phrase.