Erreur : Unknown column 'grille' in 'where clause'

bonjour quelqu'un pourrait m'aider a régler ce probleme voici mon code:
<?php
$db = mysql_connect('xxxxxxxx','xxxxxxx','xxxxxxx');
mysql_select_db('xxxxxxxx',$db);

$Req = "SELECT * FROM calgrille WHERE grille and ok='non' ORDER BY grille LIMIT 1";
$Res = mysql_query($Req,$db);
while($data = mysql_fetch_array($Res))
$numgrille=$data['grille'];

$Reqa = "SELECT * FROM membre WHERE arrete='non' and membre.pseudo not in (select pseudo from participants WHERE grille=$numgrille)ORDER BY pseudo";
$Resa = mysql_query($Reqa) or die ("Erreur : ".mysql_error());
echo"<center><font size='2'color='brun'>".$i++." Pseudo</font></center>";
while($Obja = mysql_fetch_array($Resa))
{echo "<center><font size='2'color='orange'>".$i++."- ".$Obja['pseudo']."</font></center>";

}?>

merci de votre aide
footballpronos