function TbsSheetCheck() {
		if (count($this->OtbsSheetSlidesDelete)>0) $this->RaiseError("Unable to delete the following sheets because they are not found in the workbook: ".(str_replace(array('i:','n:'),'',implode(', ',$this->OtbsSheetSlidesDelete))).'.');
		if (count($this->OtbsSheetSlidesVisible)>0) $this->RaiseError("Unable to change visibility of the following sheets because they are not found in the workbook: ".(str_replace(array('i:','n:'),'',implode(', ',array_keys($this->OtbsSheetSlidesVisible)))).'.');
	}