Simply place this code where you wish it to appear.
<b>Statisics</b><br />
Last Registered: [last_registered]<br />
Total Members: [total_members]<br />
Application Places: <script type="text/javascript">
/*<![CDATA[*/
var available = 100;
var current = [total_members];
var total = available-current
document.write(total);
/*]]>*/
</script>
The members remaining idea came from stickycarrots on Dev.