Public Function UPCA2UPCE(ByVal UPCA As String) As String
    '
    ' Convert UPC-A to UPC-E format
    '
    ' Written by Glenn J. Schworak (www.schworak.com)
    '
    Dim ValidDigits As String
    Dim Mfg As String
    Dim Prod As String
    Dim x As Integer
    
    If Len(UPCA) <> 12 Or (Left(UPCA, 1) <> "0" And Left(UPCA, 1) <> "1") Or _
       InStr(1, Mid(UPCA, 5, 8), "0000") < 1 Then
        UPCA2UPCE = "INVALID"
    Else
        Mfg = Mid(UPCA, 2, 5)
        Prod = Mid(UPCA, 7, 5)
        If Right(Mfg, 3) = "000" Or Right(Mfg, 3) = "100" Or Right(Mfg, 3) = "200" Then
            ValidDigits = Left(Mfg, 2) & Right(Prod, 3) & Mid(Mfg, 3, 1)
        ElseIf Right(Mfg, 2) = "00" Then
            ValidDigits = Left(Mfg, 3) & Right(Prod, 2) & "3"
        ElseIf Right(Mfg, 1) = "0" Then
            ValidDigits = Left(Mfg, 4) & Right(Prod, 1) & "4"
        Else
            ValidDigits = Left(Mfg, 5) & Right(Prod, 1)
        End If
        UPCA2UPCE = Left(UPCA, 1) & ValidDigits & Right(UPCA, 1)
    End If
End Function