SSRS Graph: First date of every month.

I have a records which having  which are loaded onto the the database with a time stamp called report_date.

Want a bar graph to be generated for a 3 month period.Bar should show first report of every month.

Example: Report between jun 2012 - Sept 2012

Bars should be shown for the first load of the month. the dates are: 3rd Jun 2012,5th july 2012,16th aug 2012 (<- these dates are first entry of the month)