Business Rule - Notify on edit issue

Hi SupportCenter, been a while, hope you are all well?!?

I am trying to set up a Business Rule to send an customised email to a given person when the Group is changed from, lets say any one of 10 categories to this specific one that I want it to trigger on.

This works fine in this scenario

Edit Support Request
Change Group to Escalation
The Business rule has the Business Rule customised email template
It sends an email as expected.

The problem I have is if someone goes into this Request and changes any other value it triggers the rule as the Group is Escalation and sends another email. It doesn't take into account that the value is already Escalation.

I don't want to use the Notification to send to users of a Group as you can't set a specific customisation for the email per group using this method, it would apply to all emails to groups.

How do I resolve this?

Cheers

Rich