如何在表单字段中显示旧的提交值?

I created a form by RSForm. I have two textbox in it. First textbox name is km1 (new_km) and second textbox name is km2 (old_km). In the first time, user will fill km1 field (new_km) by her car kilometer number. When the user recourse again and fill the form, km2 (old_km) must shown value that user entered it in previous recourse. Please guide me? Best regards.

Right, I know, my English is very bad. sorry.

Like this image: http://persianupload.com/kleeja/do.php?imgf=141839395854871.jpg

I personally use session for that...

Your html:

<?php
 session_start();
 if(!isset($_SESSION['something'])) $_SESSION['something'] = '';
?>
<input type="text" name="something" value="<?php $_SESSION['something']?>"/>

Your receiver php:

<php
 session_start();
 if($_POST['something']) $_SESSION['something'] = $_POST['something'];
?>