Line Chart Advice : trying to drill down....

Hi,
I have a relatively simple report that is using a graph which plots total costs by month. I am trying to link this to another report using the drill down on the chart values. I want to be able to pass the chart series (which is in the form of 653...652...651 etc etc) to a parameter in another report. For example If I click on the green line it passes the series value of 653 and if I click on the blue series it passes 654 etc etc.
Can this be done and how?????
I have been playing round with the expressions but just cant seem to link it. It links fine if I hard code a series but then that obviously passes the same value for all the series on the graph!!
Any help would be great!