如何在VB.net中的webbrowser控件上设置具有身份验证（用户名和密码）的代理？

我已经在使用InternetSetOption和wininet更改Internet Explorer的代理设置，因为webbrowser控件也使用它，但是我如何添加它，以便它可以使用需要身份验证的代理用户：pass？ 这是我的密码：

Public Structure Struct_INTERNET_PROXY_INFO
    Public dwAccessType As Integer
    Public proxy As IntPtr
    Public proxyBypass As IntPtr
End Structure


Private Sub setProxy(ByVal strProxy As String)
    Const INTERNET_OPTION_PROXY As Integer = 38
    Const INTERNET_OPEN_TYPE_PROXY As Integer = 3

    Dim struct_IPI As Struct_INTERNET_PROXY_INFO

    struct_IPI.dwAccessType = INTERNET_OPEN_TYPE_PROXY
    struct_IPI.proxy = Marshal.StringToHGlobalAnsi(strProxy)
    struct_IPI.proxyBypass = Marshal.StringToHGlobalAnsi("local")

    Dim intptrStruct As IntPtr = Marshal.AllocCoTaskMem(Marshal.SizeOf(struct_IPI))

    Marshal.StructureToPtr(struct_IPI, intptrStruct, True)

    Dim iReturn As Boolean = InternetSetOption(IntPtr.Zero, INTERNET_OPTION_PROXY, intptrStruct, System.Runtime.InteropServices.Marshal.SizeOf(struct_IPI))
End Sub
Private Declare Auto Function InternetSetOption Lib "wininet.dll" (ByVal hInternet As IntPtr, ByVal dwOption As Integer, ByVal lpBuffer As IntPtr, ByVal lpdwBufferLength As Integer) As Boolean

这就是我想更改代理时使用的：

setProxy("ip:port")

那么，如何添加对身份验证的支持呢