Start dialog from javascript when new entity is creating and pass data to the response

I have a dialog process. As I know I can start dialog only when one of record selected. Besides I try to run dialog from javascript and if I open one of record it works fine. here is my javascript code snippet

var url = "http://"+ window.location.host + parent.Xrm.Page.context.prependOrgName("/cs/dialog/rundialog.aspx?DialogId={" + dialogId +"}&EntityName=" + entityName + "&ObjectId=" + entityId);

url = encodeURI(url);
window.open(url);

but if I try to open dialog from javascript when a new record is being creating, I have an error "Dialog warning". Can I start dialog when creating a new record?

And how can I pass a value from javascript to dialog response?