Need suggestions concerning B.O.M table structure

[Autoeng]

I am soliciting suggestions on what would be the best way to construct a bills of materials table. I currently have a db in place to document and control engineering changes to the products we produce. This database consists of one form which is a traditional data entry form, a subform (again traditional data entry) and another subform (this one in table format). In the table format subform the users enter everything affected by the change, (end product, sub assemblies and parts). As a change might affect many end products the users like to group the affected end products, sub assembles and parts together and then separate them from other end products by inserting a blank row.

Example: Green Widget (end product)
Green plastic widget body (sub assembly)
Raw green plastic (part)
(blank row)
Red Widget (another end product)
Red plastic Widget body (another sub assm)
Raw red plastic (another part)

I know that this can't be good for my database. If I could left indent, center, right indent, bold and italic in a table I could get them to stop the blank row insertion as they could modify format to indicate structure, however I haven't identified a method to do this inside of a form.

Does anyone have any suggestions so that I don't have all of these blank rows hogging up space, memory and resources in the table.

Thanks to all that are willing to submit suggestions,
Autoeng