rrdtool from private scripts

[joel at carnat.net]

Hi,

I wrote a script to get alert about CPU loads on a windows server using
SNMP (no I don't want to / can't install the hobbit client on the server
;). The status is returned OK (green before 50%, orange from 50 to 75 and
red over 75).

The thing is, there is no graph done (yet).
I would like a graph that would show the load average variation.

(how) can the script be used to fill a RRD database ?
Should the load average value be returned in a special variable ?

Thanks for help,
   Jo