External Interface and Mouse Clicks

I'm new to writing ActionScript.
I am working in .NET (C#) environment using AxShockwaveFlashObjects.
I am simply trying to react to a mouse click on the Flash ActiveX Control.

I have inserted the code in a layer only used for script:
import flash.external.ExternalInterface;
var mouseListener:Object = new Object();
var boolMouseDown:Boolean = false;
mouseListener.onMouseDown = function ()
{
boolMouseDown = true;
};
mouseListener.onMouseUp = function()
{
if (boolMouseDown)
{
ExternalInterface.call("MouseClicked", "NavigateToURL", " http://www.adobe.com");
boolMouseDown = false;
}
};
Mouse.addListener(mouseListener);

I get the MouseClick event in my C# code. The problem is that I get TWO of the same event ??
Can someone tell me why or how I should be doing this to get only one event.
Thanks,
Steve