vbs中怎么读取UTF-8编码的文件

vbs中如何读取UTF-8编码的文件
Function Encode(filePath)
Set stm = CreateObject("Adodb.Stream")
stm.Type = 2
stm.mode = 3
stm.charset = "utf-8"
stm.Open
stm.LoadFromFile filePath
Encode = stm.readtext
stm.close
End Function

Msgbox Encode("D:\a.txt")