Joe,
You don't need the field in your table. Calculate it whenever you need it
either in a calculated control on a form, or in a query. Although
counterintuitive to new users, the reasons are:
- It's faster to calculate the value on-the-fly than look it up from the disk.
- It takes VBA code to save a calculation to a field, since you can set a
form control's ControlSource to a calculation expression OR to a field name,
but not both.
- If the factors involved in the calculation are changed outside the context
of your form, your stored calculation will be WRONG.
Using a relational database is a paradigm shift from a "flat file" approach
such as might be implemented in a spreadsheet, where you'd have a column for
every field you need in one place. Relational databases break up the data
into multiple tables, with a minimum of duplication--customer info is stored
ONCE in a customer table, order header information (custid, orderdate,
salesrepid, etc.) is stored ONCE in an Orders table. In related tables, all
you need to store is the primary key of another table (a foreign key in the
related table) to "Access" its fields by linking the tables in a query.
Hope that helps.
Sprinks