Const CHUNKSIZE = 8192

Dim xEncode As New XceedBinaryEncoding

Call xEncode.License( "your license key" ) 

Dim lOffSet As Long
Dim lFileSize As Long
Dim vaBytesRead As Variant
Dim vaEncoded As Variant 

Set xEncode.EncodingFormat = New XceedBase64EncodingFormat 

lOffSet = 0 ' We must track the current offset 

On Error Resume Next 

lFileSize = FileLen("c:\temp\source.txt")

While lOffSet < lFileSize
  'bEndOfData will be true if the current offset + CHUNKSIZE exceeds the end of the file. 

  vaEncoded = xEncode.ReadFile("c:\temp\source.txt", lOffSet, CHUNKSIZE, bfpEncode, _
                               (lOffSet + CHUNKSIZE >= lFileSize), vaBytesRead)  

  If Not IsEmpty(vaEncoded) Then 
    ' You now have a portion of encoded data you can use. 
    ' For example, transfer it, process it, etc. 
  End If 

  lOffSet = lOffSet + vaBytesRead 
Wend 

If Err.Number = 0 Then
  MsgBox "Finished encoding file to memory." 
Else
  MsgBox Err.Number & " " & Err.Description 
End If