If you are using Access 2k or later, you can use conditional formatting. You
can specify an Expression like
[FieldA]=0 And [FieldB]=0
You can also use code in the on format event of the section containing the
controls.
Me.txtFieldA.Visible = Not ([FieldA]=0 And [FieldB]=0)
Me.txtFieldB.Visible = Not ([FieldA]=0 And [FieldB]=0)