[jQuery] How to activate autocomplete in this case

[wesley...@gmail.com]

Hi,
i have a question,
how to manually fire the autocomplete event?

<input type="text" id="acTxt" />
<span class="pTxt">aa</span>,
<span class="pTxt">bb</span>,
<span class="pTxt">cc</span>,
<span class="pTxt">dd</span> ...

$(document).ready(function(){
        $("#acTxt").autocomplete(theUrl, {
                minChars: 2,
                matchContains: true,
                max: 20
        });

        $(".pTxt").click(function() {
                $("#acTxt").val($(this).html()? $(this).html():'');
        });
});


if the user click on SPAN with class 'pTxt', the innerHTML of the SPAN
will place in the textbox,
how to activate the autocomplete without pressing UP, DOWN, PAGE UP,
and ....?