Thanks, Jeff.
When I tried to upload the .t3x file, typo3 complained (wrongly imho) that my php maximum file size might be set too low and refuses to upload it. I then decided to upload it by gFTP to typo3conf/ext and to typo3conf/ext/cal but I do not know how to get typo3 to realise its presence !
If there is a howto or something, please let me know.
Thanks,
Calum