Is this the right place for this?

I've got a client who wants to continue using MessageBot to maintain his email list. His site uses frames, and currently when the submit button is clicked, the MessageBot page opens in the bottom frame. We want it to open in a new browser window. Do any of you know how I sould code the button to do this? AFAIK, there is no support from MessageBot. Here is the Q&D code as it is now.

<!-- Start http://MessageBot.com -->
<FORM ACTION="http://MessageBot.com/cgi-bin/list/add.cgi">
<p style="margin-top: 0; margin-bottom: 0">Mail List members are eligible to win extra special drink or food specials!<br>
<input name="email"><br>
<input type="hidden" name="list" value="Gaspars">
<input type="submit" value="Join Our List">
<br>
<font size="1">Powered by: <a TARGET="_blank" href="http://MessageBot.com/">MessageBot</a></font></font><font size="1">
</p>
</FORM>
<!-- End http://MessageBot.com -->

I can't begin to figure this out.

Thanks if you can help ... thanks anyways if you can't.

Dale