Ok, well I couldn't figure out how
to do what you suggest, but I have found a way to automatically run the search
index. It ain't elegant, and it ain't clever - but it works, and it doesn't
require cron.

Basically the search is run in a
javascript pop-up that is triggered when a visitor hits the page containing
the script.

Only it's a self-closing pop-under,
contrived to run (almost) invisibly behind the main page.

The javascript to put in the head
of the page you choose should look something like this:

<script type="text/javascript" language="JavaScript"><!--

function goPopUnder() {

ThePopUnder=window.open("http://www.mysite.com/cgi-bin/fmsearch/admin4.cgi?ftc=web","","width=100,height=100,top=1000,left=1000,scrollbars=0,resizable=0,toolbar=0,location=0,menubar=0,status=0,directories=0,alwaysLowered=1");
ThePopUnder.blur();

closetime = 20;

if (closetime)
setTimeout("ThePopUnder.close();", closetime*1000);

}

//--></script>

I think the line
beginning ThePopUnder=window.open
and ending alwaysLowered=1");
should all be on one line.

Then you need to
place into the same page the body attribute: onLoad="goPopUnder()"

Obviously admin4.cgi?ftc=web
would be substituted for whichever of the search scripts you are employing.
This is the mySQL database version.

I've set the closetime
to 20
seconds to ensure that enough time is given to complete the indexing before
the hidden window closes.

That's it. Provided someone happens
upon your page once in a while, your search will be automatically reindexed.

I've chosen to combine this idea with the pseudo-cron refered to above, so
my site only gets indexed once every 24 hours.