Worksheet Change Problem

[Pflugs]

I am trying to write an event to change the value in a cell after the cell
above it is changed to a certain value. Both cells are validation lists, and
the lists in the second cell are dependent on the value in the first cell.
All the rest of the data in the sheet (thousands of cells) are related to
these cells, and it seems that this recalculation stops the change event.

The code:
Private Sub Worksheet_Change(ByVal Target As Excel.Range)

If Target.Address = "$B$1" Then
Application.EnableEvents = False
Application.Calculation = xlCalculationManual
If Target.Value > 30 Then
Range("B2").Value = "Fillet Root Side"
End If
Application.EnableEvents = True
Application.Calculation = xlAutomatic
End If

End Sub

The code works great on a test sheet. I can't understand why it doesn't
work in the sheet with all the data. Can anyone provide a solution or
workaround?

Thanks,
Pflugs