XML source question

Below you will see a piece of an xml file that I'm using as a data source. It functions fine - no problems - for the grid.

<PricingNodes xmlns="http://markets.midwestiso.org/tibco/xml" MISO_RefId="19-OCT-2006_09_00" PJM_RefId="19-OCT-2006_08_55">
<PricingNode name="AEC" LMP="25.88" source="MISO"/>

I have two questions:

1) Is there a way to refresh the data (re-read the XML) once every 5 minutes?

2) While the name/lmp/source populate the grid just fine, is there a way (like in a table.response method to get the two values (PJM_RefId and MISO_RefId) and assign them to a javascript variable so I can display them on the page?

Any help would be appreciated.