function OpenXML_CTypesPrepareExt($FileOrExt, $ct='') {

		$ext = $this->Misc_FileExt($FileOrExt);

		$this->OpenXML_CTypesInit();
		
		$lst =& $this->OpenXmlCTypes['Extension'];
		if (isset($lst[$ext]) && ($lst[$ext]!=='') ) return;

		if (($ct==='') && isset($this->ExtInfo['pic_ext'][$ext])) $ct = 'image/'.$this->ExtInfo['pic_ext'][$ext];

		$lst[$ext] = $ct;

	}