trim custom field text value and show (…)

building on keatch’s answer you only need to trim if its longer the 25 chars so:

$trim_length = 25;  //desired length of text to display
$custom_field = 'my-custom-field-name';
$value = get_post_meta($post->ID, $custom_field, true);
if ($value) {
    if (strlen($value) > $trim_length)
        $value = rtrim(substr($value,0,$trim_length)) .'(...)';
 echo $value;
}