Monthly Snapshot of Historical Open Reqs

Summary

Need Help to determine how to create a Monthly Snapshot in one Report

Content

I am reporting on Trends Analysis, and i need to capture what our Reqs that were sourced at the end of each month for the past two years. I have come up with the attached but i need to run it individually for each month end (I used a combination of a sample report established by Taleo with some added items i needed for this the report) I am having a hard time coming up with a formula that will date stamp the last date of each month and record it and trend out the open reqs by a division.