CLR-Based Trigger? Recursive Trigger? Common Table Expression?

Hey,

I'm new to this whole SQL Server 2005 thing as well as database design and I've read up on various ways I can integrate business constraints into my database. I'm not sure which way applies to me, but I could use a helping hand in the right direction.

A quick explanation of the various tables I'm dealing with:
WBS - the Work Breakdown Structure, for example: A - Widget 1, AA - Widget 1 Subsystem 1, and etc.
Impacts - the Risk or Opportunity impacts for the weights of a part/assembly. (See Assemblies have Impacts below)
Allocations - the review of the product in question, say Widget 1, in terms of various weight totals, including all parts. Example - September allocation, Initial Demo allocation, etc. Mostly used for weight history and trending
Parts - There are hundreds of Parts which will eventually lead to thousands. Each part has a WBS element. [Seems redundant, but parts are managed in-house, and WBS elements are cross-company and issued by the Government]
Parts have Allocations - For weight history and trending (see Allocations). Example, Nut 17 can have a September 1st allocation, a September 5th allocation, etc.
Assemblies - Parts are assemblies by themselves and can belong to multiple assemblies. Now, there can be multiple parts on a product, say, an unmanned ground vehicle (UGV), and so those parts can belong to a higher "assembly" [For example, there can be 3 Nut 17's (lower assembly) on Widget 1 Subsystem 2 (higher assembly) and 4 more on Widget 1 Subsystem 5, etc.]. What I'm concerned about is ensuring that the weight roll-ups are accurate for all of the assemblies.
Assemblies have Impacts - There is a risk and opportunity impact setup modeled into this design to allow for a risk or opportunity to be marked on a per-assembly level. That's all this table represents.

A part is allocated a weight and then assigned to an assembly. The Assemblies table holds this hierarchical information - the lower assembly and the higher one, both of which are Parts entries in the [Parts have Allocations] table.

Therefore, to ensure proper weight roll ups in the [Parts have Allocations] table on a per part-basis, I would like to check for any inserts, updates, deletes on both the [Parts have Allocations] table as well as the [Assemblies] table and then re-calculate the weight roll up for every assembly. Now, I'm not sure if this is a huge performance hog, but I do need to keep all the information as up-to-date and as accurate as possible. As such, I'm not sure which method is even correct, although it seems an AFTER DML trigger is in order (from what I've gathered thus far). Keep in mind, this trigger needs to go through and check every WBS or Part and then go through and check all of it's associated assemblies and then ensure the weights are correct by re-summing the weights listed.

If you need the design or create script (table layout), please let me know.

Thanks.