VBA code for Microsoft Excel to convert 15-digit Salesforce.com record ids to their 18-digit checksum version. Use by adding into a new module in the Excel VBA code editor. NOTE: I did not write this - but can't quite remember who/where I got it from. If it's yours, please let me know and I'll update to provide attribution.

Excel VBA - SFDC 15 to 18

Function FixID(InID As String) As String
    
    If Len(InID) = 18 Then
        FixID = InID
        Exit Function
    End If
    
    Dim InChars As String, InI As Integer, InUpper As String
    Dim InCnt As Integer
    
    InChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ012345"
    InUpper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    
    InCnt = 0
    
    For InI = 15 To 1 Step -1
        InCnt = 2 * InCnt + Sgn(InStr(1, InUpper, Mid(InID, InI, 1), vbBinaryCompare))
        If InI Mod 5 = 1 Then
            FixID = Mid(InChars, InCnt + 1, 1) + FixID
            InCnt = 0
        End If
    Next InI
    
    FixID = InID + FixID

End Function