I've been asked this before and I didn't think it could be done with the current version. But it just occurred to me that you might be able to use the timestamp function for this. It allows you to track the time at which any item begins. Timestamps are always appended to a file called "timestamps.csv" located in the data folder. Consequently (I think), each time the participant answers and re-answers the question, you would get a timestamp value to indicate so. Voila.

For more detail, see timestamp in the users guide or online here:

http://www.empirisoft.com/medialab/h....htm#timestamp
http://www.empirisoft.com/medialab/h...#datatimestamp

Would be curious to hear if that turns out to be a useable approach.