Automatically Updating Graphs based on Date

Hi,

I have a number of tables which I update on a weekly basis and I've created a number of graphs based on these values, but I only want the graphs to show the previous full months complete data rather than the most recent update. Also, I'd like the graphs to automatically update from the table at the start of each month for the preceding months complete data without me having to re-select the data range each month.

Can any show me how this is done please or point me towards the right direction?