I have just found an easy solution. I first changed the example numbering from "(2)" to "2" and then did "update field" on the entire document. This changed the cross reference numbers from ((2)a) to (2a). Then I changed the example numbering back to "(2)". As long as I don't do another "update field" on the reference numbers, they are staying as (2a). yeah! This is not a full solution but I guess easiest.