I assume he's already talking about custom properties. We have a custom property on our part files for quantity. It's linked to a note in the title block on our parts drawing template. I think CADmiester is looking for a macro that would read the BOM on an assembly drawing and update the custom property field with the quantity from the BOM. Of course, unless he is using no standard parts (nuts, bolts, etc.) and has no common parts across different jobs/machines/products, he'll probably want to be able to skip certain files. This should be an easy enough macro to write. I've already got one that accesses the text in the BOM, but it only reads it as text in a dumb table, by rows and columns. I'm not at work right now, but I would imagine that there's a way to find the part/subassembly file bound to a row of the BOM through the API.
Cadmiester, what is your familiarity with VBA? Would a good starting point and a few pointers get you to where you can figure it out, or are you needing a plug-and-play solution?
It sounds to me like you need this functionality for assemblies with more than a few parts. However, if I'm wrong and you only care about a few critical parts then faq559-1232 may be able to help you some.
Have a great day!