Check Criteria Beforesave

Hi profs,

I am new to yii and i have developped an online scheduler

The sceduler is almost ready to go live

and i have one/two last things to check out:

I have a class termin and here i have the fields:

id(int),datum (Date),employeename(Varchar),starttime(Time),endtime(Time),customername (varchar)

Bevore i create or update the termin i have to check if the employee has another termin

at the same date between the starttime and the endteime. How can I check this in a yii function

or get an activerecord wich i can stepthrough with a foreach loop or something.

My first concern was to write a function to the termin class and call it in the beforesave function just like this but here i cannot find any hints to how i can this get to work:

	protected function beforeSave()



			//   $this->Datum=strftime('%Y-%m-%d', strtotime(str_replace("/", "-", $this->Datum)));



        $this->Datum = strtotime ($this->Datum);

        $this->Datum = date ('Y-m-d', $this->Datum);		

			return TRUE;


		else return false;



	public function checkTerminvalide($datumc,$mitarbeiterc,$startzeitc,$endzeitc){

	$criteria=new CDbCriteria;



	$criteria->params=array(':startzeit'=>{$startzeitc}, ':endzeit <= {$endzeitc});

	$post=Post::model()->find($criteria); // 


return ?


can anybody help ?