Function btoa$ (s As String)
    Const B64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    Dim c1 As _Byte
    Dim c2 As _Byte
    Dim c3 As _Byte
    Dim c4 As _Byte
    Dim i As Long
    Dim As String Buffer
    For i = 1 To Len(s) Step 4
        c1 = InStr(B64, Mid$(s, i + 0, 1)) - 1
        c2 = InStr(B64, Mid$(s, i + 1, 1)) - 1
        c3 = InStr(B64, Mid$(s, i + 2, 1)) - 1
        c4 = InStr(B64, Mid$(s, i + 3, 1)) - 1
        If c2 > -1 Then Buffer = Buffer + Chr$(((c1 * 4 + c2 \ 16) And 255))
        If c3 > -1 Then Buffer = Buffer + Chr$(((c2 * 16 + c3 \ 4) And 255))
        If c4 > -1 Then Buffer = Buffer + Chr$(((c3 * 64 + c4) And 255))
    Next i
    btoa$ = Buffer
End Function