' Base64 编码函数
Function BASE64ENCODE(strText As String) As String
    Dim arrData() As Byte
    arrData = StrConv(strText, vbFromUnicode)
    
    Dim objXML As Object
    Dim objNode As Object
    
    Set objXML = CreateObject("MSXML2.DOMDocument.6.0")
    Set objNode = objXML.createElement("b64")
    
    objNode.DataType = "bin.base64"
    objNode.nodeTypedValue = arrData
    BASE64ENCODE = objNode.Text
End Function

' Base64 解码函数
Function BASE64DECODE(strBase64 As String) As String
    Dim objXML As Object
    Dim objNode As Object
    
    Set objXML = CreateObject("MSXML2.DOMDocument.6.0")
    Set objNode = objXML.createElement("b64")
    
    objNode.DataType = "bin.base64"
    objNode.Text = strBase64
    BASE64DECODE = StrConv(objNode.nodeTypedValue, vbUnicode)
End Function