HELP! HELP! HELP! need to generate a specific report.

Hi,
I've been trying to generate a report to track sales for every product on every month to monitor which ones are fast moving or slow moving on the shelf.
Unfortunately I have not been able to do that. Is there a special calculation that I have to do(how?)? What do I need to do to get this burden of my shoulder? My database is created in ms-access and I have crystal reports 8.5. I hope someone can help me on this... can someone help me please? any given help shall be greatly appreciated.