jQuery event to trigger action when a div is made visible

I’m using jQuery in my site and I would like to trigger certain actions when a certain div is made visible.

Is it possible to attach some sort of “isvisible” event handler to arbitrary divs and have certain code run when they the div is made visible?

I would like something like the following pseudocode:

$(function() {
  $('#contentDiv').isvisible(function() {
    alert("do something");
  });
});

The alert(“do something”) code should not fire until the contentDiv is actually made visible.

Thanks.