how to fetch fresh html for an Elabel map object

Hey all, i am working with google maps and a function in the Elabel
that i am using to put data on a map.

In the docs for the Elabel, there is a function
label.setContents(html) where html is what will go inside the
Elable.

it looks like this:

var weather_table_one = new ELabel(new GLatLng(35.5,-102), <%=
@weather_table_html %>, "style1");
map.addOverlay(weather_table_one);

what i need to do is update the data in the map every time the map
moves ( with a listener ) and every 20 seconds or so.
So i thought i would use a PeriodicalExecuter where the function is
setContents(html) but i don't know how to fetch that html

any tips would be greatly appreciated.

sk