Q:

Microsoft Access 2003 - Expression Builder

When the user click the add button on the form, everything else is saved except for the field that uses expression builder in its control source. I understand the control source is the main source of saving the field into the table. How do i (or can i?) actually save the field into the record source? 

A:

This goes by design - you cannot use an expression as the control source and then expect Access to write to a database column that is nowhere specified. 
You could use an expression for the control's default but for being able to write to a dateabase column you need to make the column the control's source. 
Another possibility is using the form's "Current" event to fill the field with the expression's result. 

