I'll try to be more specific:

I have a two column TwwDbGrid and a two column TIBOQuery
(qryTest) with two float-fields.
The OnChange-event-handler of Field1 consists of:
{==================}
qryTest.FieldByName('FIELD2').AsFloat := 2 *
qryTest.FieldByName('FIELD1').AsFloat;
qryTest.InvalidateRows;
{==================}

So the value of Field2 is filled with the value of Field1
multiplied by 2.

Back to the grid. If I change the value of the column Field1, and
tap the Tab-key, then the value of column Field2 shows the
correct value, so the OnChange-event-handler works fine. However,
the record isn't posted yet. If I then change the value of the
column Field1again an EAccessViolation shows up with the text:
Access violation at address 0057497C in module 'Infas.exe'. Read
of address 0000000C.

If I change the value of Field1 and then POST the record, all
works fine and I can change the value of Field1 again without any
exceptions.

tia,

Gerard

On Thu, 10 Jul 2003 13:07:00 -0700, you wrote:

>> I use a TwwDbGrid and a TIBOQuery.
>> In the OnChange-event of Field1 I change the value of Field2 that
>> is depending on Field1.
>> The change of Field2 is not visible in the grid.
>> So I use a call to InvalidateRows in the OnChange-event. Then the
>> change of Field2 is instantly visible in the grid.
>> But when I change Field1 a second time, without posting it first,
>> an exception is raized.
>> How do I solve this?
>
>You eed to be more clear here.
>
>At the very least let us know what exception was raised.
>
>Also, I can't really tell what it is you are doing.
>
>Jason
>
>
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_________________________

Gerard J.M. Houtenbos
DoubleWood Software