Clay - thanks for the lead, but I'm still stuck!! - I'm fairly new to Infopath! - I'm using 2003.
I've tried both the following xpaths in the table History field hoping to get the Select_approve_option to appear - but no good.
1. current()/../my:Initial_PIN_Review/my:Review_history/my:History = ../../my:Select_approve_option
2. current()/my:myFields/my:Initial_PIN_Review/my:Review_history/my:History = /my:myFields/my:Initial_PIN_Review/my:Select_approve_option
Initial_PIN_Review is a group containing the repeating table Review_history and the Select_approve_option (an option button) - my:History is a field in the table.
Again thanks for your help.