Private Sub Worksheet_Calculate()
Dim dProfit As Double
dProfit = Me.Range("A1").Value
If dProfit > 600 Then
MsgBox "Profit has risen to " & Format(dProfit, "#,##0.0"), vbExclamation
ElseIf dProfit < 500 Then
MsgBox "Profit has fallen to " & Format(dProfit, "#,##0.0"), vbCritical
End If
End Sub