Eliminar caracteres UTF-8 de cuatro bytes en ASP/VBScript clásico (relacionado con MySQL)

Esto debería funcionar:

Function UTF8Filter(strString)
    On Error Resume Next
    For i = 1 to Len(strString)

        charCode = AscW(Mid(strString, i, 1))
        If charCode > 32 AND charCode <= 127 then   ' here was OR 
            'Append valid character'
            strString = Mid(strString, i, 1)
        End If
    Next

    UTF8Filter = strString
    On Error Goto 0
End Function

Función actualizada:

Function Remove4ByteUFT8(strString)
    Set objRegEx = CreateObject("VBScript.RegExp")
    objRegEx.Global = True   
    objRegEx.IgnoreCase = True
    objRegEx.Pattern = "/[\xF0-\xF7].../s"

    Remove4ByteUFT8 = objRegEx.Replace(strString, "")
End Function