Change in backlog priority triggers mass email alerts

Hi,

So I have a backlog and I have some backlog items assigned to staff for one reason or another. 

I then insert a backlog item fairly near the top. This has the effect of changing the computed backlog priority number for each of the items below the newly inserted. 

I have the email alert "A change is made to a work item that is assigned to me"

Problem is i don't want a change in backlog priority to trigger mass emails to all people affected. 

I've had a look at the Alert Filters and can't see an option to say I.E

AND Backlog Priority Has NOT Changed.

I only have the options Changed from and Changed to and Changes.

Thanks

James