Need help in writing an alerting rule

Hi All,
I am new to prometheus tool. Need some help with writing an alerting rule.

I have an existing rule with the following expression

expr: ( resourcelimit_current / resourcelimit_param ) * 100 > 80

I want to modify it such that if the resourcelimit_param=0, it shouldn’t trigger an alert. Is there a way I could achieve this? Any help would be much appreciated!