Question

I want a text box to contain data which is a calculation based on 2 other control field values – only if it’s value is null (ie the current value of the column in the database is null).

So I entered =([control1]*[Control2])/1000 in the expression builder for the default value property – however the result always shows the textbox to be empty (even tho control2 and control2 contain values).

How can I achieve this? Can such an operation only be done in code-behind ie VB??

thanks,

KS

Answer 1

I think you’re talking about a control bound to a field in the form’s record source. And when the underlying field is Null, you want the control loaded with your calculated value.

If that interpretation is correct, you can do it from the form’s On Current event.

If IsNull(Me.txtYourTextBox) Then
    Me.txtYourTextBox = (Nz(Me.control1) * Nz(Me.Control2)) / 1000
End If

That will load the computed value into the text box, allow the user to change its value if desired, and store the value to the bound field when the record is saved.

If the bound field is not Null, its value will be displayed in the text box without alteration by the On Current code.

Is that what you want?