Thanks George. with a little tweaking this has solved my problem .
I couldn't use the MonitoringObjectPath as the identifier as this isn't always populated in an Alert.
Instead I used the ToplevelHostentityid property which seems to have done the Trick many thanks for your help on this i'm sure you saved me days of headache

Probably worth noting this was identified as as a bug in the MP and is being rectified in the next release