VBAで、テキストファイルの文字コードを自動判定します。

Function CharSetOfText(Path)
Dim fso
Dim File
Dim htmlfile
Set fso = CreateObject("Scripting.FileSystemObject")
Set File = fso.GetFile(Path)
File.Name = File.Name & ".txt"
Set htmlfile = GetObject(File.Path, "htmlfile")
Do While htmlfile.readyState <> "complete"
  Application.Wait Now + TimeSerial(0, 0, 1)
Loop
CharSetOfText = htmlfile.CharSet
File.Name = fso.GetBaseName(File.Name)
End Function