You are trying to fill in form data on another site when they click on a referal link on your site, correct?
If so, does the other site use PHP for their forms? If they do, you could pass the form data as query string variables as long as they had the input variables set correctly.
In other words, if they have a form with the following input tag:
<input type='text' name='test' value='<?php echo $test; ?>'>
and you pass the "test" variable in the query string like:
<a href='http://www.refer_site.com/form.php?test=<?php echo urlencode($test); ?>'>Click HERE!</a>
It would populate the text field automatically. This assumes some cooperation from the refer site and that they use PHP as well.
John Cornett