How to define time for timeout for users?

[toplisek]

I have simple code for logged users which is stored in db in table on server:

$query2 = "INSERT INTO users_session
SET
`SESSID` = '{$SESSID}',
`SESSusername` = '{$user}',
`SESSIP` = '{$_SERVER['REMOTE_ADDR']}',
`SESStype` = 'logged',

$_SESSION['logged'] = TRUE;
$_SESSION['SESSID']= $SESSID;
$_SESSION['SESSusername'] = $user;
$_SESSION['SESSIP']= $_SERVER['REMOTE_ADDR'];
$_SESSION['SESStype']= 'logged';
mysql_query ($query2,$link)
or die ("Insert error:".mysql_error());

How to define variable :
`TimeOut` = ;
$_SESSION['TimeOut']= ' ';


Need help if this is possible