Alert using percentages

I've been searching for a solution to set up an alert for file shares based on percentage usage, but I haven't found a way to make it dynamic.

What I want is an alert that triggers when a file share reaches 80% of its total capacity. The challenge is that if I increase the file share size after reaching the 80% threshold, the alert won’t be useful anymore because it’s tied to a fixed size.

Ideally, I would like the alert to automatically adjust to 80% of the new file share size, whatever that may be at the time, without having to set up a new alert with the updated byte value. Is there a way to set the alert as a percentage of the current file share size so that it dynamically updates as the size changes? Or maybe a query that would work in this situation?

Start by reviewing Azure Monitor alerting and the available file share capacity metrics. Determine whether an alert can use a percentage of current capacity or a dynamic query, and consider the issue addressed when the supported approach or limitation is clearly documented.