This may seem silly, but after struggling with this for a while hopefully it will be useful to others.
MediaLab does not automatically generate a responses.xls file, you have to create one! I was under the impression it did and was searching for it forever. Just create a new workbook in Excel and save it in your experiment folder as responses.xls. The first column needs to be labeled variable, the second as value, and the third as skipto.
