Tracking usage of the "go back" function

I would like to run an experiment in which participants will first make a choice between a number of alternatives (scale response item) and then, on the next page, will receive additional information. We want to allow participants to go back to their previous choice, if they want to, and change their responses. How can I track who actually goes back and change their responses given the new information?

I'm aware of the "allow go back" option in the questionnaire file but I don't see how to have the usage of this tool recorded in the data file. Is there a way I can accomplish this? Thank you!

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 [I]timestamp[/I] 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:

[URL="http://www.empirisoft.com/medialab/help/queparameters.htm#timestamp"]http://www.empirisoft.com/medialab/h....htm#timestamp[/URL]
[URL="http://www.empirisoft.com/medialab/help/data_faq.htm#datatimestamp"]http://www.empirisoft.com/medialab/h...#datatimestamp[/URL]

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