Average values using offset

Hey guys,

I am trying to create a dynmaic reporting tool that can average monthly metrics so I can display them in a changing, dynamic graph. I currently have the first month(December '12) working just fine but the tool deosnt capture the data from the next two months (January '13 and February '13). I think it has something to do with my offset function but can't seem to find the error. Any help would be much appreciated, thanks!


[ATTACH]Example File[/ATTACH]