请问怎么用InternetReadFile把网页源代码读到一个byte数组里

如下面的一段程序：

Option Explicit
Private Declare Function InternetOpen Lib "wininet.dll" Alias "InternetOpenA" (ByVal sAgent As String, ByVal lAccessType As Long, ByVal sProxyName As String, ByVal sProxyBypass As String, ByVal lFlags As Long) As Long
Private Declare Function InternetOpenUrl Lib "wininet.dll" Alias "InternetOpenUrlA" (ByVal hInternetSession As Long, ByVal sUrl As String, ByVal sHeaders As String, ByVal lHeadersLength As Long, ByVal lFlags As Long, ByVal lContext As Long) As Long
Private Declare Function InternetReadFile Lib "wininet.dll" (ByVal hFile As Long, ByVal sBuffer As String, ByVal lNumBytesToRead As Long, lNumberOfBytesRead As Long) As Integer
Private Declare Function InternetCloseHandle Lib "wininet.dll" (ByVal hInet As Long) As Integer

Function GetCode(Url As String) As String
    Dim Hwnd1 As Long
    Dim Hwnd2 As Long
    Dim Hwnd3 As Long
    Dim Hwnd4 As Long
    Dim Str1 As String * 1024
    Const INTERNET_FLAG_NO_CACHE_WRITE = &H4000000
    Hwnd1 = InternetOpen("VBTagEdit", 1, vbNullString, vbNullString, 0)
    Hwnd2 = InternetOpenUrl(Hwnd1, Url, vbNullString, 0, INTERNET_FLAG_NO_CACHE_WRITE, 0)
    If Hwnd2 <> 0 Then
        Do
            Hwnd4 = InternetReadFile(Hwnd2, Str1, 1024, Hwnd3)
            GetCode = GetCode & Mid$(Str1, 1, Hwnd3)
        Loop While (Hwnd3 <> 0)
    End If
    InternetCloseHandle (Hwnd2)
End Function

返回的是string类型的。。。怎样才能返回byte类型呢？