Fire Brick QTY

I am looking for a way to show a 1/2 qty on a bom.

Contarctors will cut 9" brick in half to 4.5" & use each half,but say I model 80 4.5"cut brick, the BOM should only show 40 9"brick (this is the size that they come in).

Any suggestions on how I could do this.

The 9" brick is in a design table with the 3 sizes & the 4.5cut is a derived config of the 9"...if that helps.

Thanks!SolidworksBill Of Materials