libraries/tbs/plugins/tbs_plugin_opentbs.php
function MsExcel_SheetIsIt($FileName) {
		$this->MsExcel_SheetInit();
		foreach($this->MsExcel_Sheets as $o) {
			if ($FileName=='xl/'.$o->file) return true;
		}
		return false;
	}
function MsExcel_SheetIsIt($FileName) {
		$this->MsExcel_SheetInit();
		foreach($this->MsExcel_Sheets as $o) {
			if ($FileName=='xl/'.$o->file) return true;
		}
		return false;
	}
Check if the file name is a subfile corresponding to a sheet.