I use the below code to write code to query a web method in a specified interval.
now in the this.Poll function I have to do
this.tmo = setTimeo
I provided an answer for a similar question today in which I created a polling class from scratch. You may want to adopt it for yourself. In the sake of not duplicating, here's a link a link to said question:
Poll the Server with Ajax and Dojo *
* Despite the title, my solution offers both "vanilla" and Dojo styles.