Mime 64 encoder in VBS

Attribute VB_Name = "mime64"
Option Explicit

Function Base64Encode(InputStream As String) As String

Dim Base64Alphabet As String
 Base64Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

Dim OutputStream As String
Dim ByteDecVal As Integer
Dim BitBinVal As Integer
Dim ByteGroup As String
Dim ByteGroupBinStream As String
Dim Padding As String
Dim BytePtr As Long

Dim Index As Integer

Do While InputStream <> ""
    ByteGroup = Left$(InputStream, 3)
    Do While ByteGroup <> ""
        For Index = 7 To 0 Step -1
            ByteDecVal = Asc(Left$(ByteGroup, 1))
            BitBinVal = BIT(ByteDecVal, Index)
            ByteGroupBinStream = ByteGroupBinStream & Trim$(Str$(BitBinVal))
        Next Index
        ByteGroup = Mid$(ByteGroup, 2)
    Loop
    If Len(ByteGroupBinStream) < 24 Then
        Padding = String$((((Len(ByteGroupBinStream) / 8) - 3) * -1), "=")
        ByteGroupBinStream = ByteGroupBinStream & String$(Int(24 / Len(ByteGroupBinStream)) + 1, "0")
    End If
    Do While ByteGroupBinStream <> ""
      BytePtr = Val(BitToDec("00" & Left$(ByteGroupBinStream, 6))) + 1
        OutputStream = OutputStream & Mid$(Base64Alphabet, BytePtr, 1)
        ByteGroupBinStream = Mid$(ByteGroupBinStream, 7)
    Loop
    OutputStream = OutputStream & Padding
    ByteGroupBinStream = ""
    InputStream = Mid$(InputStream, 4)
Loop
Base64Encode = OutputStream
End Function


Function BIT(ByteDecVal As Integer, Index As Integer) As Integer
Dim bIndex As Integer
bIndex = 2 ^ Index
BIT = IIf((ByteDecVal And bIndex) > 0, 1, 0)
End Function


Function BitToDec(BitStr As String) As Long
Dim Results As Long, CiDx As Long
  For CiDx = 8 To 1 Step -1
    Results = Results + (Val(Mid$(BitStr, CiDx, 1)) * (2 ^ (8 - CiDx)))
  Next CiDx
  BitToDec = Results
End Function