aquí tienes algo que te podría servir. Rehice todo tu codigo, espero que sepas agradecerlo.
Saludos
Código PHP:
Ver original<?php
include_once 'lib.php';
$result = mysql_query("SELECT id_stock, codigo, descrip, pre_min, pre_may, disponibles FROM stock where activo = '1'", $conexion); ?>
<form name="borrar" method="post" action="vender_prod.php">
<table border="2">
<tr>
<th>ID</th>
<th>Codigo</th>
<th>Descrip</th>
<th>Prec.Min</th>
<th>Prec.May</th>
<th>Disponibles</th>
<th></th>
<th style='border: none'></th>
<th>Cantidad</th>
</tr>
<?php
$i = 0;
?>
<tr>
<td><?php echo $row['id_stock'] ?></td>
<td><?php echo $row['codigo'] ?></td>
<td><?php echo $row['descrip'] ?></td>
<td align="right"><?php echo $row['pre_min'] ?></td>
<td align="right"><?php echo $row['pre_may'] ?></td>
<td align="center"><?php echo $row['disponibles'] ?></td>
<td><input id="chk_<?php echo $i ?>" name="seleccion[]" type="checkbox" value="<?php echo$row['id_stock'] ?>" class="chk"/></td>
<td style="border: none"></td>
<td><input id=txt_<?php echo $i ?>" name="text[<?php $row['id_stock'] ?>]" disabled="disabled" type="text" style="width: 60" class="txt"/></td>
</tr>
<?php
$i++;
}
?>
</table>
<br />
<input type="submit" name="submit" value="enviar">
</form>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$(".chk").change(function(){
var comentario = $( '.txt', $( this ).parents ( 'tr' ) );
if( $(this).is(':checked')){
comentario.removeAttr('disabled');
} else {
comentario.attr('disabled', true);
}
});
});
</script>