Using JavaScript, is there a way to detect whether or not an external script (from a third-party vendor) has completely loaded?

The script in question is used to pull in and embed the markup for a list of jobs and, unfortunately, doesn't make use of any variables or functions. It uses document.write to output all of the content that gets embedded in my page.

Ideally, I'd like to display some kind of loading message while I'm waiting for the external script to load, and if it fails to load, display a We're sorry, check back later... message.

I'm using jQuery on the site, but this external script is called before I make the jQuery call.

Here's what the document.write stuff from the external script looks like:

document.write('<div class=jt_job_list>');

document.write(

    <div class=jt_job jt_row2>

        <div class=jt_job_position>

            <a href=http://example.com/job.html>Position Title</a>

        </div>

        <div class=jt_job_location>City, State</div>

        <div class=jt_job_company>Job Company Name</div>

    </div>

);