You are unable to promote a repeating table so you cant get the dates from a repeating table that way, your best option is to push the date out into a separate list, it's your choice whether to link them back to the initiating form or not. Then you can report on the dates however you like. You will have to use SP web services to submit your date to the list.... Something similar to doing this is here: http://www.infopathdev.com/forums/p/26246/99173.aspx#99173