Let's say your select list has options 1, 2 and 3
<select>
<option value="1">One</option>
<option value="2">Two</option>
<option value="3">Three</option>
</select>
On your link, you could use option as a parameter.
<a href="contact.php">
becomes
<a href="contact.php?option=1">
Then, on the select list on the conatct page, click the dynamic button in properties, and on 'select value equal to' at the bottom, type $_GET['option'] or whatever you called the parameter
(sorry, but I can;t test this at the moment as my computer is being difficult, apologies in advance for any typos/errors)