How to find out the difference between messages of today and last week at Grafana

I want to create an alert at Grafana which finds out the difference of messages between today and last week ?

From 1h to Now I have alert When : sum() OF query(A,1h,now) IS BELOW 1

I want to get the calculate the difference between last ween and now and create an alert if it’s BELOW 1. I searched a lot from internet but could not find how to compare two dates .

Could you please help me to fix that issue ?

Thank you for your helps.