OK I'll try and explain what it is I am doing here. I have a line graph which counts events over time-- specifically comparing semester fall 2006 to fall 2007 and uses weeks of semester as the Category group and semester as the series group. I want to shot the percentage of change over time between the two semesters. So if Fall 2006 week 2 had 5 events and Fall 2007 week 2 had 10 events I want to show this increase as a percentage (50%)-- I also want to be able to show the reverse-- Fall 2006 has 10 events and Fall 2007 has 5 events, etc. Can someone point me in the right direction??