Hope this helps
<a href="click.asp?url=$1" target=_"blank" class="SmlLinks">$1</a>
And the Hyperlink & description tag to something like
<a href="click.asp?url=$1" target="_blank" rel="nofollow" class="SmlLinks">$2</a>
Depending on how your click.asp page works and where it is relative to the forum. You could get a bit funkier with the search patterns if you want to detect if its an external link, but be careful if you are not sure about regular expressions.