[jQuery] Query on jQuery object?

[jQuery] Query on jQuery object?


This may obvious, but I haven't seen any examples that fit what I'm
trying to do. In many places in my code, I will select an element once
into a var and make necessary changes. What I can't seem to figure out
or find documentation on is querying on an existing object.
Here's what I have to do now:
$().ready(function(){
$("#mydiv").click(function(){alert('hello')});
$("#mydiv .childdiv").css("font-weight", "bold");
}
seems a tad inefficient to make two trips through the DOM.
Here's what I would like to do:
$().ready(function(){
var mydiv = $("#mydiv");
mydiv.click(function(){alert('hello')});
// here's where I'm lost
// find all the element identified as "childdiv" and set its css
mydiv("#childdiv").css("font-weight", "bold");
// is there a way to do this with out multiple trips to the DOM?
}