How to enable the 'click' and its function in the tags function?

How to enable the 'click' and its function in the tags function?

I write the code as the follows to make it appear in the tag_handler when
I click the .fly li, but it doesn't work: I cannot add the tags and delete
the tags.
One more question is how can I disable click to the tag after click for
once and re-enable after delete the tag in the tag_handler. Thanks.
function add_tag(that){
var singleValues = $(that).html();
$("#tag_handler").append(singleValues);
}
$(".fly li").click(function(){
add_tag(this);
});