Checksum Calculation on String

[jetcat]

I need help in creating a 'checksum' from a string using the following conventions:

1) Add the 1st byte of the string to a checksum byte
2) Clear Bit 7 of the above result
3) Set Bit 6 of the result
4) Add this result to the next byte of the string
5) Repeat steps 2-4 until last byte of string is read.

Please Help! I don't know how to get started?!

Try this one...

Option Explicit

Private Sub Form_Load()
    Debug.Print CalcChecksum("Hello World!")
End Sub

Public Function CalcChecksum(S As String) As Byte
    Dim chk As Byte ' Final Checksum
    Dim T As Long   ' Char-pointer...
    
    ' Step 1
    chk = Asc(Mid(S, 1, 2))    ' Get first Char value
    
    ' Initialize counter
    T = 1
    While T < Len(S)
       
        ' Step 2
        chk = chk And 127   ' Bitwise operation. Clear bit 7 (127 -> 0111 1111)
        
        ' Step 3
        chk = chk Or 64     ' Bitwise operation. Set bit 6 (64 -> 01000000)
        
        ' Increase counter...
        T = T + 1
        
        ' Step 4
        chk = Asc(Mid(S, T, 1)) + chk
    Wend
    
    CalcChecksum = chk
End Function

Hope it works for you...