how can I update expression value to another control

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anj - 21 Mar 2005 04:07 GMT

Dear All
Thanks in advance!
I want to use expression to calculate the total value in
a "control A" on "form A" which is based on a "Table A".
But the calulated value does not update its value to the
corresponding field on "Table A". Is it possible to use
another unbound "control B" on "form A" to calculate the
derised value with expression and then using some code its
calulated value is automatically entered onto the "control
A" and that is reflect onto the corresponding fields
on "Table A" ?
Or there any other method that can used?

Thanks a lot!

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John Vinson - 21 Mar 2005 07:28 GMT

>Dear All
>Thanks in advance!
>I want to use expression to calculate the total value in
>a "control A" on "form A" which is based on a "Table A".

The simplest way is to use a textbox in the Form Footer with a control
source of =Sum([Field A]); you need to sum the *table field* not the
form control.

>But the calulated value does not update its value to the
>corresponding field on "Table A". Is it possible to use
[quoted text clipped - 3 lines]
>A" and that is reflect onto the corresponding fields
>on "Table A" ?

Storing derived data such as this in your table accomplishes
three things: it wastes disk space; it wastes time (almost
any calculation will be MUCH faster than a disk fetch); and
most importantly, it risks data corruption. If one of the
underlying fields is subsequently edited, you will have data
in your table WHICH IS WRONG, and no automatic way to detect
that fact.

Just redo the calculation whenever you need it, either as a
calculated field in a Query or just as you're now doing it -
in the control source of a Form or a Report textbox.

John W. Vinson[MVP]

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