Two Sub Summaries Plotted On Line Graph By Month To Show Progression

[DanMarks]

I'm new to graphs on FileMaker so not sure how this one would work, so any ideas would be very much appreciated.

 

My client has a returns table, anything that is returned is entered into this table with the item title, department, return value and date returned. 

 

I needed to produce a report which highlights the value of items returned by department by month. 

I have done this by doing two sub summaries, first the month (http://help.filemaker.com/app/answers/detail/a_id/790/~/creating-a-sub-summary-by-month), then by the department. This used a count summary field of the return value. This works as expected.

 

But the client would like a line graph which plots the cost (Y axis) against month  (X axis) with a different colour line per department showing on the same graph. I can't as yet work out a way to do this.

 

Thanks in advance!
Dan