I've a nine measure passage that repeats with an exception of one measure. So the 1st run plays measure 2A and 2nd run plays measure 2B. Is there notation that indicates this? Or will I have to write out both 9 measure passages with the correct measure 2?
You can use 1st & 2nd time repeats - thanks to Wikipedia - Repeat Sign for the image...
So you score your first 8 bars just once, then use the two alternatives for the 1st & 2nd time round. You can extend this to 3rd, 4th etc if necessary.