XHTML to Cals table conversion

Hi,

I was just looking for a stylesheet, which can transform XHTML to Cals
tables.
But I couldn't fin anything useful on the net.
Has anyone done such an XSLT yet? I just read that it is very difficult
to write one
because of the raspan behavior of XHTML tables....
Am thankful for any hint :)
Otherwise I'll have to try to write it myself :(

with best regards,
Roman