add an entry with javascript

hi!

i want to write a javascript for inserting entries into my google
calendar.

i've read, when you are using the calendar api in a web application,
you have to athenticate via the "AuthSub" interface.
i've donethe AuthSubRequest correctly and now i want to send data to my
calendar.
what do i have to do with the token, which is appended to my url?
http://localhost/GoogleCalendar/XmlHttpUpload.html?token=.................


here the important part of my sourcecode:

xmlHttp = XMLHttpRequest();

xmlHttp.open('POST',
'http://www.google.com/calendar/feeds/default/private/full', true);
xmlHttp.setRequestHeader("Content-type", "application/atom+xml");
xmlHttp.send(xmlEntry);

xmlEntry is just a string with all the entry-data in xml format.

all i get back is the error msg:
"this feed is read-only"

what am i doing wrong? do i use the false url? which url do i have to
use when i want to add the entry with an web application?

everything seems to be so easy with the java client library, but i have
to use javascript.

i really hope, someone of you can help me out. i've spent several days
geeting my problem fixed, but i cannot find any solution.

thanks in advance,
chris