Validating a Form - How to set values on Dropdown Boxes?

[eluser]pistolPete[/eluser]
How about that:

Code:

function your_callback()
{
     $day = $this->input->post('day');
     $month = $this->input->post('month');
    
     if($month == 2 && $day > 30)
     {
          return FALSE;
     }
    
     return TRUE;
}