<form name="f1" method="post"
action"ton_fichier.php"> <table border="1" align="center" width="896">
<select name="cat"
onchange="javascript:scanSelect('mes donnees',this.options[this.selectedIndex].value)">
<option value="0" selected> --> A SAISIR <-- </option>
<option value="idcat1">GB-a</option>
<option value="idcat2">GB-b</option>
<option value="idcat3">GB-c</option>
<option value="idcat4">GB-d</option>
<option value="idcat5">GB-e</option>
<option value="idcat6">GB-f</option>
<option value="idcat7">PE-a</option>
<option value="idcat8">PE-b</option>
</select>
<select name="sscat">
<option value="0">--> A SAISIR <-- </option>
</select>
</form>
<input type="submit" value="submit">
<input type="hidden" name="processmode" value="1">
</body>
</html>
apres dans ton_fichier.php tu va récupérer $cat etc...