jQuery Grid Plugin - jqGrid

I have a simple jqgrid works using an asp.net handler code file and an asp.net page, but I need a dropdownlist button on the asp.net page such as Default.aspx when changed selected value will make the jqgrid to reload a different data. Could not find such topic on the search;  I apprecaite your support. When I use autopostback=true the grid just disapears. What to add please to make this possible I mean between js script, handler code and the Default.aspx page?