Automatic total sum from child form to main form

[eyalco]

I need to store a "calculation" which involves values from child records - it is a receipt storing totals from the receipt details.
The record is bound and I need it to update it's totals when each item in receipt is inserted.
I guess I'm looking for a form event which will operate (the after update is not good).

Thanks.

 

[MarkK]

It's not generally advisable to store a calculation on child records, since in doing so you design in a dependency that anytime and anywhere a record is changed, added or deleted you have to remember to update some dependent value.
Rather, on a main form you can bind the value of a textbox to something like this...

=DSum('SumField', 'YourTable', <filtered for the record ID in the main form>)