How to get calculation results to store in the related table

[jeanweaves]

I have a form ("Orders") with a subform ("Orders Details"). I have "Subtotal" and "SalesTax" fields on the form that calculate those figures from the subform. The calculations work fine on the form but the results do not show up in the related table. The manually entered "Shipping Cost" does show but not the fields that calculate. What am I doing wrong?

[pbaldy]

Generally:

http://allenbrowne.com/casu-14.html

[jeanweaves]

So if I shouldn't be storing the order subtotal and sales tax in the orders table, how or where does Access store the information entered in the Orders form?

[June7]

Enter raw data, do calcs as needed.

Aggregate data should never be stored, unless there is some sort of archiving process. Another Allen Browne article http://allenbrowne.com/AppInventory.html.

Save the sales tax rate in the order record if there is possibility the rate will change and don't want existing records affected by newer rate. But calculate the tax amount in query or in textbox.

[pbaldy]

The rule of thumb is not to store data that can be calculated from other data. You would calculate the subtotal from the detail records.

I take care of an accounts receivable app designed by another developer with similar header/detail tables. He stored the sum of the detail records in the header record. Despite code designed to keep them in sync, I've had to create a nightly process that checks for instances where they aren't (where the total of the detail records doesn't match the value in the header). Users have an almost magical ability to get around your code. I think they do the 3-finger-salute to exit the program in my case.

[jeanweaves]

Thanks for the input. I'll take another look at the design and make some changes.