i am using a javascript to popup a modal form as below

window.showModalDialog('Default.aspx?main_model=' + main_model + '&main_serial=' + main_serial ,'','dialogHeight:450px; dialogWidth:500px; edge: Raised; status: Yes; scroll:no; resizable:no; center:yes; help:no;');

the modal form has a dropdownlist in it, and when i set the autopostback= true, to handle the dropdown selectedindexchanged event, it pop up a new window instead of refresh on the modal form.......


How can i solved that?