A host ExcelDna add-in loading and unloading another add-in

Host Add-In

<DnaLibrary Name="Host Add-In" Language="CS" RuntimeVersion="v4.0">
<Reference AssemblyPath="System.Windows.Forms.dll"/>
<Reference Name="Microsoft.Office.Interop.Excel" />
<![CDATA[
using System;
using ExcelDna.Integration;
using System.Windows.Forms;
using Excel = Microsoft.Office.Interop.Excel;

public class HostAddIn: IExcelAddIn
{

	private static string xll_path = @"Z:\UnloadXll\Add-In\add-in.xll";

	public void AutoOpen()
	{
		Excel.Application XL = (Excel.Application)ExcelDnaUtil.Application;

		XL.RegisterXLL(HostAddIn.xll_path);

		double now = (double)XlCall.Excel(XlCall.xlfNow);
            	XlCall.Excel(XlCall.xlcOnTime, now, "UnloadAddIn");
	}

		
	public void AutoClose()
	{

	}

	public static void UnloadAddIn()
	{

		object removeId = XlCall.Excel(XlCall.xlfRegister, HostAddIn.xll_path, "xlAutoRemove", "I", ExcelMissing.Value, ExcelMissing.Value, 2);
            	object removeResult = XlCall.Excel(XlCall.xlfCall, removeId);
            	object removeUnregister = XlCall.Excel(XlCall.xlfUnregister, removeId);

		MessageBox.Show("The add-in has been disabled.", "Unload Add-In");
	}

}
]]>
</DnaLibrary>