Complexity in Posting Payments Using an Update Query

[Dalan]

I'm not certain if this is doable in the manner explained below, but
I'm certain that there have been Access developers who have done
something similar. So whatever insight and assistance that can be
provided will be much appreciated.

There is a separate Update Query (well several) that consolidate
various goods from separate tables for access and selection on a
sales/order invoice form. The data which is available is the TagNo,
ItemDescrip, Quantity and Price. Running another Update Query to post
the sold information (SoldDate and PriceSold) back to the respective
tables works fine for single items only, where there is one SoldDate,
one PriceSold and one corresponding IDTagNo.

The problem that I have attempted to resolve is related to Bulk items
where there is one main form/table with two subforms/tables - one for
purchases and one for sales. The Bulk sales are of course multiple
postings. For example the main form will contain information regarding
the product, such as hats, with purchases entered separately on a
subform, and the sales entered on another subform. The hat main form
will have a single IDTagNo and of course each entry on the subforms
have another ID number. One of the benefits of running the Update
Query for the single items mentioned above, is that if there are any
changes made it will be updated along with the new postings the next
time it is run. It seems that this cannot work for the Bulk items
because of the subform and multiple postings, or can it? What criteria
could be used?

Any thoughts or suggestions would be welcomed.

Thanks, Dalan