function getCompositionToDelete()
{
	var compositionCheckbox = $$(".presta_checkDelete");
	
	var id_checked = '';
	for( var i=0 ; i<compositionCheckbox.length ; i++ )
	{
		if( compositionCheckbox[i].checked )
		{
			id_checked += 'id_compositions[]=' + compositionCheckbox[i].value + '&';
		}
	}
	
	if( id_checked.length > 0 )
	{
		id_checked = id_checked.substr(0, id_checked.length-1);
	}
	
	return id_checked;
}