Calcualted Fields in Forms

[Guest]

How do I insert calculations in forms so that the fields in the related table
get updated?
For, e.g. to calculate tax in the [Tax] field as a function of the [Amount]
field and a fixed percentage say 10%, so that such a calculation is
automatically carrid out in the form and the [Tax] field in the related table
is updated.

 

[Nikos Yannacopoulos]

The universal rule is, if it can be calculated then you should not store
it at all, just calculate it again whenever required for another
calculation, or for display or printing purposes.

Generally, you can use a control's Control Source property to bind it to
a table field, in which case the data in it gets stored in the table, or
you can use it to enter an expression, so the value in it is calculated
on the basis of other data, but not stored in a table. If you want both
a calculation and a storing, you neet to use other means for one or the
other; the most common approach is to bind the control for storing,
while a macro or some VB code is used to perform the calculation, fired
from some form event, like the Before Update / After Update / On Change
event of (an) other control(s).

HTH,
Nikos