You can use the page header section's Format Event Procedure:
In Design view, double-click on the property for the Format Event in the
Page Header section, then click the ellipse (...)
Private Sub PageHeaderSection_Format(Cancel As Integer, FormatCount As
Integer)
Me.LineYouWantToHide.Visible = (Me.someControl = someValue)
End Sub
I ran a quick test, and I'm not sure why, but I couldn't directly access a
field in the recordset from this sub, so I settled for accessing the value
in a control that was bound to the desired field. If the report doesn't
display the field, you could make it invisible.
HTH
Paul Johnson