Adding The Src In Iframe Tags

adding the src in iframe tags. the problem to resolve looks like this:

<script type="text/javascript">
/*
Display the daily schedule in an inline frame.
Daily schedules are stored in the files
sunday.htm through saturday.htm.
*/
document.write("<iframe src ='weekday.htm'></iframe>")
</script>

Instructions say where weekday is the text string returned by the weekDay() function. I do have weekDay() function but I don't know how to include it into the iframe.