jQuery Grid Plugin - jqGrid

hi, experts, on my aspx page, I have infragistics tab control and there are 3 tabs.

when the tab is clicked, it post back to server and run something in the event controller.

on each tab, I have the jqgrid (free version one, no wrapper) and it shows different kind of data. 

now, I only know to use web handler to load data to the jqgrid, it means when the user access the page, it loads all data to the 3 jqgrids in 3 different tabs by once. How can I control to load the data to the jqgrid from code behind?

what I want to have : when user access the page, it only loads only the data for 1st tab

when user clicks the 2nd tab, it loads only the data for 2nd tab