I working a a standard purchase request sytem but am having trouble with coming up with a total cost. The form is built off of two tables. One for requests (tblPR) and one for Items (tblItems) joined by a unique identifier. In order to come up with a total cost I need to sum the individual item costs (from items table) and add the shipping cost from the request table. I can do this in a query group by RequestId, sum ItemCosts and add Shipping. But that puts a lock so that I may not add new records on my form. Suggestions appreciated.
You could take a look at the Northwind database that comes as a free sample with Access. The Orders form does pretty much what you are asking
for I think.
The Freight cost is stored in the Orders table. But the sample also shows how the subtotal is calculated on the subform then carried formward to the main form. Note that the subtotal is never actually stored (because it can always be derived)