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 Calculating a Code 128 Barcode Checksum in Access Basic Home > Barcode Basics > Application Notes > AppNote004 This bit of Access Basic (same as Visual Basic) will calculate a Code 128 Modulo 103 checksum. Barcode fonts from different publishers may map some characters to different locations, so be sure to check. ```Function Format_Code128 (InString As String) As String Dim Sum As Integer, i As Integer Dim Checksum As Integer, Checkchar As Integer Dim MyString As String, CVal As Integer ' ' Initialize running total with value of ' Subset B start character ' Sum = 104 ' ' Scan the string and add character value times position ' For i = 1 To Len(InString) ' ' Copy one character from InString position i to MyString ' MyString = Mid\$(InString, i, 1) ' ' Get the numeric value of the character and subtract ' 32 to shift (the space character, ASCII value 32, has ' a numeric value of 0 as far as Code 128 is concerned) ' CVal = Asc(MyString) - 32 ' ' Add the weighted value into the running sum ' Sum = Sum + (CVal * i) Next i ' ' Calculate the Modulo 103 checksum ' Checksum = Sum Mod 103 ' ' Now convert this number to a character. This conversion ' takes into account the particular mapping of the font ' being used (this example is for the font published by ' Azalea Software. ' If Checkdigit = 0 Then Checkchar = 174 ElseIf Checkdigit < 94 Then Checkchar = Checkdigit + 32 Else Checkchar = Checkdigit + 71 End If ' ' Now format the final output string: start character, ' data, check character, and stop character ' MyString = Chr(162) + InString + Chr(Checkchar) + Chr(164) Format_Code128 = MyString End Function```

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