function check_select(id)
{
    var select = document.getElementById(id);
    var input = document.getElementById(id + '_custom');
    
    if (   !select
        || !input)
    {
        return false;
    }
    
    if (select.value == 'other')
    {
        input.removeAttribute('readonly');
    }
    else
    {
        input.setAttribute('readonly', 'readonly');
    }
}