I suspect you really want to display a rate (how many impulses per hour/day etc) rather than a count.
To the above options I'd like to add option 0: Dont worry about retrieving the past count so long as your arduino doesnt restart too often. ( Every counter has an overflow point so your code just has to deal with a count that goes backward now and again)
See my post on how to convert a counter into a rate at http://community.thingspeak.com/forum/thingspeak-plugins/converting-counter-values-to-rate-of-change/ Doubtless it can also be done in a Matlab visualisation nowadays.