var NewWindow = null;

function CheckRedundant()
{
    if (NewWindow != null) 
	{
        NewWindow.close();
        NewWindow = null;
    } 
}

function ExternalWindow( File, WindowWidth, WindowHeight ) 
{
	CheckRedundant();
	Options = 'width=' + WindowWidth + ',height=' + WindowHeight + 
			',toolbar=0,scrollbars=1,location=0,statusbar=0,menubar=0,resizable=1,left=40,top=40';
	NewWindow = window.open(File,'',Options);
}