Late binding and delegate method signatures

[Matt]

I'm trying to use late binding to automate Excel from C#
so as to run with multiple versions of Excel, and am
hoping to avoid referencing any Excel PIA in my project.
But I need to add a C# event handler to do some processing
before Excel closes. Ildasm shows the handler Invoke
like this:

void(class Microsoft.Offic e.Interop.Excel .Workbook,bool& )

My current attempt at adding a late-bound event
handler looks like this:
{
....
//Startup Excel
Type tExcel = Type.GetTypeFro mProgID("Excel. Application");
eApp = Activator.Creat eInstance(t);

// Get type for the close event handler
Type tDel = eApp.Assembly.G etType
("Microsoft.Off ice.Interop.Exc el.AppEvents_Wo rkbookBeforeC
loseEventHandle r",false,tru e);

// Create a delegate for the event
Delegate myDel = Delegate.Create Delegate
(tDel,this,"myH andler",true);

// Register the handler
EventInfo ei = tExcel.GetEvent ("WorkbookBefor eClose");
ei.AddEventHand ler(eApp,myDel) ;
}

private void myHandler(objec t workbook, ref bool Cancel) {
// Do processing here when workbook is closing
....
}

The CreateDelegate fails with an error
"error binding to target method". I'm presuming that's
because it expects a
Microsoft.Offic e.Interop.Excel .Workbook parameter and not
a generic object as I have. Is there any way in C# to
have the CreateDelegate accept a method with a generic
object parameter instead of the Excel.Workbook class?

Thanks for any help!