An ADD-On for an existing code

Every time the cell value in BG1 changes I want a message box displaying the value of BG1 ( which will usually be like "BEWARE 940" etc. This I want to incorporate in the following existing code:-

Dim OldValue1
Dim OldValue2
Dim OldValue3
Dim OldValue4
Dim OldValue5


Private Sub Worksheet_Calculate()
If [D1] <> OldValue1 Then
    Application.EnableEvents = False
        [G1] = [G1] + 1
        OldValue1 = [D1]
    Application.EnableEvents = True
End If
If [D2] <> OldValue2 Then
    Application.EnableEvents = False
        [G2] = [G2] + 1
        OldValue2 = [D2]
    Application.EnableEvents = True
End If
If [D3] <> OldValue3 Then
    Application.EnableEvents = False
        [G3] = [G3] + 1
        OldValue3 = [D3]
    Application.EnableEvents = True
End If
If [D4] <> OldValue4 Then
    Application.EnableEvents = False
        [G4] = [G4] + 1
        OldValue4 = [D4]
    Application.EnableEvents = True
End If
If [D5] <> OldValue5 Then
    Application.EnableEvents = False
        [G5] = [G5] + 1
        OldValue5 = [D5]
    Application.EnableEvents = True
End If
End Sub

Please help me if you can....

What's in BG1???