function MethodFromNativeDll (DllPath, EntryName, RtnT, ParmT) {
    var asmName = new clr.System.Reflection.AssemblyName();
    asmName.Name = "NativeDll";

    var asmBuilder = 
        clr.System.AppDomain.CurrentDomain.DefineDynamicAssembly(
            asmName, clr.System.Reflection.Emit.AssemblyBuilderAccess.Run);

    var modBuilder = 
        asmBuilder.DefineDynamicModule("NativeDll");

    var methdBuilder = 
        modBuilder.DefinePInvokeMethod(EntryName, DllPath,
        clr.System.Enum.Parse(clr.System.Reflection.MethodAttributes.Final.GetType(),
            'Public, Static, PinvokeImpl'),
        clr.System.Reflection.CallingConventions.Standard, RtnT, ParmT, 
        clr.System.Runtime.InteropServices.CallingConvention.Winapi, 
        clr.System.Runtime.InteropServices.CharSet.Ansi);

    methdBuilder.SetImplementationFlags(
         clr.System.Enum.Parse(clr.System.Reflection.MethodImplAttributes.IL.GetType(),
         methdBuilder.GetMethodImplementationFlags().ToString() + ", PreserveSig"));

    modBuilder.CreateGlobalFunctions();
    mthdInfo = modBuilder.GetMethod(EntryName);
    return mthdInfo;
}

//Type for return value.
var RtnT = clr.System.Type.GetType("System.Int32");

//Type array for param types.
var ParmT = host.newArr(clr.System.Type, 2);
ParmT[0] = clr.System.Type.GetType("System.IntPtr");
ParmT[1] = clr.System.Type.GetType("System.Int32&");
//For ByRef vars, append a & after the type name.

//Object array for params.
var Parm = host.newArr(clr.System.Object, 2);
Parm[0] = sp.DesktopWindow().HWnd;
Parm[1] = 0;

//Get method
var Mthd = MethodFromNativeDll("user32.dll", "GetWindowThreadProcessId", RtnT, ParmT);

//Invoke method.
var v = Mthd.Invoke(null, Parm);

sp.MessageBox(Parm[1], v);