One of the varialbes you have avialable for creating custome columns is "Earnedperweek" over the last 5 weeks. Now there are are ways to set up your dkp system to take advantage of that to give you an attendance number over that 5 week period but its a pain to put it mildly as there are several steps that have to be done by hand.

It would be much simpler to get the same result if there was a variable such as "Raidsattended" that gave a count of how many raids a particular player had been in over that 5 week period.

Not sure where your at as far as providing attendance information for 30,60,90 day periods but this seems like a fairly small add on that would allow work arounds in the mean time.