[Evolution] Can't access my calendars with writing permission

[roy nico free fr]

Hello Community,

I have several calendars .ics files, stored on a server. I have the 
following problems :
* I don't see how i can access the files , thur FTP protocol. In "new 
calendar", if i give "FTP://file_adress", the prefix is automatically 
transformed in "webcal://", and i can not access the calendars
* I can give the http-address of the file. It works, but of course, i 
can only read them, and not write on them.
* If i give the webdav-Address of the files, i can also read them, but 
not write.

Not, that with Thunderbird+lightning, everything works : i have Read and 
Write access through FTP or through Webdav.

Any idea how to make it work ?
Thanks,

Nicolas

Config :
Ubuntu 10.10