Grafana alerts : how to define specific threshold in a rule for each instance

Hi, we are working on Grafana 8.0.1.

We are looking for a solution to create a global rule that can be overrided by specific rules.
Let me explain : we have multiple instances monitored, and for each instance we have specific thresholds. Example :

For the instance A : cpu_usage_system{instance=”A”} > 10
For the instance B : cpu_usage_system{instance=”B”} > 20
For all other instances : cpu_usage_system > 30

Is there a way to create a global rule, for example cpu_usage_system > 30, where the threshold can be overrided for specifics instances ?

Thanks in advance for your help