How to place DropDownList1_selectedIndexChanged event in JSON.Parse()

How to place DropDownList1_selectedIndexChanged event in JSON.Parse()

function initialize() {
var markers = JSON.parse('<%=ConvertDataTabletoString()%>');
var mapOptions = {
center: new google.maps.LatLng(markers[0].lat, markers[0].lng),
zoom: 5,
mapTypeId: google.maps.MapTypeId.ROADMAP
};
Please help me..how to place that event in JSON.Parse method..I already
create "ConvertDataTableString()..but i want to change the location in
dropdown list..for that i placed dropdown list..please say any one....