Etwas

function getButton( e )
{
	if ( !e ) { e = window.event }
	
	var btn;
	
	if ( e.which )
	{
		switch ( e.which )
		{
		  case 1:
		    btn = 'LEFT';
		    break;
		  case 3:
		    btn = 'RIGHT';
		    break;
		}
	}
	
	if ( (e.button || e.button == 0) && e.which == undefined )
	{
		switch ( e.button )
		{
		  case 0:
		  case 2:
		    btn = 'RIGHT';
		    break;
		  case 1:
		    btn = 'LEFT';
		    break;
		}		
	}
	
	return btn;
}