BOM Calculations

I'm currently using Axapta version 4, and am frustrated by the way BOM calculations work.

We have BOMs that run to around 4 levels, and some instruments have many hundreds of line items / routes.

When I run a BOM calculation for the headline item, the end result is fine, and the costs in the Item file are populated perfectly.

Is there a way of auto calculating (and updating the Item file) the costs for all of the sub-assemblies (also BOMs)? From the research that I've done, it appears that I have to go into each separate sub-assembly and update the BOM / Item file cost.

Is there a better way?

Thanks

Michael