OEM Grid Control Question

I'm trying to setup metric/alerts to exclude the UNDO_TBS from being monitored for the tablespace percent full condition. However, I'd like to have "All other tablespaces" to be monitored as before, which means "warning" > 85% and "critical" > 95%.  

The way I set it up was to add another condition under the "Tablespace Full Percentage" metric for UNDO_TBS such as that the warning threshold is > 101 and the Critical threshold is also > 101. However, this does not seem to work since I'm still getting those alerts on UNDO_TBS. Grid Control did not complain about this setup.  

Any suggestion? We're using 10.2.0.2 Grid Control.  

Thanks

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