Configuring 10g OEM for USER DEFINED ALERTS

[Shailesh]

Hello,

I want to set up some USER DEFINED METRICS in 10g. The restriction
with USER DEFINED METRICS, is the query (or function ) monitoring that
metrics should return only 1 value.
I want to find out all the segments, approaching their maximum limit.
Is it possible to achieve this functionality, using USER DEFINED
METRICS.
One of the metric present in OEM is, Tablespace_PCT_FULL. It returns
name of tablespace along with the percentage, if it is crossing
warning or critical threshold. I was trying to configure new 'USER
DEFINED METRICS', for monitoring 'segments, approaching their maximum
limit'. As query(script) for USER DEFINED METRICS can return only
value, I am not able to write query to implement my requirement. (i.e.
name of the segment and percentage of extents reached)
Does anybody know some way to do that?

Thanks,
Shailesh