var arcgisMap = { dojo: "dojoArcgis", dijit: "dijitArcgis", dojox: "dojoxArcgis" };
var dojoConfig = { //required for custom extensions to ArcGis (e.g. the cluster layer)
parseOnLoad: true,
packages: [
{ "name": "dojoArcgis", "location": 'http://serverapi.arcgisonline.com/jsapi/arcgis/3.5', packageMap: arcgisMap },
{ "name": "dijitArcgis", "location": 'http://serverapi.arcgisonline.com/jsapi/arcgis/3.5', packageMap: arcgisMap },
{ "name": "dojoxArcgis", "location": 'http://serverapi.arcgisonline.com/jsapi/arcgis/3.5', packageMap: arcgisMap },
{ "name": "Clustering", "location": '@Url.Content("~/Scripts/map/CustomArcGis/Clustering")' }
]
};dojoArcgis.require("esri.map");extremely late reply, but check out this article