Access 2007 not auto-updating calculation with bound fields

I developed an Access 2003 database with a form that has a number of bound input text fields. As the user update the value in these fields, the table is updated with the changed value. I also have an unbound textfield that displays a calculated value from the user input. This does not use the values from the textfields on the form, but directly from the table.

The Control Source of this textfield is something like:

=[field1]+[field2]+[field3]

Rather than

=txtInput1.value+txtInput2.value+txtInput3.value

In Access 2003, the calculated textfield get updated automatically as a user changes开发者_运维技巧 the bound input fields. However some of the users are using Access 2007 and they don't get the calculated field updated automatically, unless they reload the form.

It only updates automatically if I use the input textfields rather than the bound fields to perform the calculation.

I have selected "Allow this content" in the security warning. Is there anything else I can do to make it behave like in Access 2003?

Thanks