matrix master-detail problem

I'm evaluating various of .net reporting tools and founding the fastreport.net is exciting one. But when i try it, i encounter the following problem.
when matrix used as detail, the relation of datasource doesn't work. i don't know how to pass the master key to detail matrix. I browsed all of the document and search on the google and found nothing. Although i set the filter expression on the matrix, it also dosn't work. Could you pls help me?

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