Thanks again for your reply mdahlman, It's working now, I used your technique, I changed something and now it works fine, but I am facing another problem (the last one I promise ^^). All that we have calculated are the "real inclusion rate" All that I would like to calculate is "planned inclusion rate" The start is at 3 planned inclusions per quarter. And I have to calculate it with +3 planned inclusions per quarter, and I have tryed to do this alone the morning et yesterday without sucess, do you think you can help me one last time please ? =) I attached one .bmp for the explication. ^^ Thanks for your help... Post Edited by noude at 11/08/2010 13:14