It wasn't that simple.
One must edit the DataAssist search server behavior for the results page with Dreamweaver to give the fields that are searching the same column (age, in my example) a unique value. (I did MinAge and MaxAge.)
Then one must change the label, ID and name for those fields on the search page and, additionally, change the PHP that echos the values of those if set. Like this:
---------------------
<div class="lineGroup"> <label for="MinAge" class="sublabel" > Minimum Age:</label>
<div class="errorGroup">
<span>
<input id="MinAge" name="MinAge" type="text" value="<?php echo((isset($_GET["MinAge"])?$_GET["MinAge"]:"")); ?>" class="formTextfield_Medium" tabindex="6">
</span>
</div>
</div>