eugz
It is always possible to save the result of a computation - but rarely necessary and usually wasteful of space. As a matter of good programming practice in databases, you NEVER EVER store what you can recompute on-the-fly. This is because computers have cycles to burn, but the bigger your table, the more space it takes up. OK, you say, I've got a 150 Gigabyte disk, who cares about space? But that's not the space you consume.
When you have tables and search them or otherwise process them, the bigger the table, the fewer records you can fit into the disk buffer where those records are kept during the search or processing. CPUs are SO much faster than disks that you still take an advantage if you can reduce the size of the record. Because when processing linearly, you can still save time if you can fit more than one record in a disk buffer at one time.
As to how to compute this value, put the expression in the control source of the control on the form where the values are displayed. OR build a query that includes a formula for this computed value, and build the form off the query. Then just remember to disable edits of the computed value.
