Weldments question: Is there an easy way to add up all the weldment lengths, and link to BOM?

Is there a way to take the multiple lengths of a weldment and total them up into a custom property? I was thinking of using an equation, but I can't seem to link equations to cut-list properties.

FYI, I want to do this because in upper level assemblies where the weldment parts are used need to have a total length showing in the BOMs.

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