[mythtv] XMLTV tv_grab_??

[Duarte Cordeiro]

Hi,

 I'm adapting the tv_grab_es script to create a tv_grab_pt that allows ppl
from Portugal to get their program guides.

First question: the different tv_grab_xx scripts available within MythTV
setup are hardcoded ? How can I add my script to mythtvsetup ? 
And a problem:
 I grab the channel listings from
http://www.tvcabo.pt/tv_cabo_progr_canal.asp, and the program guide for each
channel from
http://www.tvcabo.pt/tv_cabo_progr_canal.asp?identificadorCanal=channel_id.
The problem is that those pages (the per channel guides) are served by a Win
SQL server who is always crashing or timing out. Also, I don't have a option
on asking for a particular day. I just get the next 7 days in a single page.
So, my question is:
  - Imagine that I can sucessefully retrieve (and parse) the information for
the 50 available channels for the next 7 days.
  - Tomorrow, I'm doing the same grabbing; but I fail to get program guides
for about 20 cannels. 
What happens with the program guides for those 20 channels that are already
in MythTV ? Are they deleted because this time there is no program info on
those channels, or may I assume that this operation is only a "add" not a
"subst" or "del" ?

Thanks for your time,

 Duarte