Reporting Grandchild Data Elements

Reporting Grandchild Data Elements

Hi all,
My data is set up so a top form called assembly uses a multi select to hold different parts. My parts form uses a subform to collect different materials that the part is made out of. 

I am able to report on the materials from the parts section but I cant do so from the assemblies section. ZOHO does not seem to realize that assemblies and materials are indirectly related. How can I set something up so that when I click on an assembly all of the materials (grandchild data) is displayed. 

Thanks!