Actually I found a custom alert that will do it.
Here it is if anyone wants it.
You need to create a Custom SQL Alert
Then add the text below:
JOIN ResponseTime ON Nodes.NodeID=ResponseTime.NodeID
WHERE ResponseTime.DateTime BETWEEN DATEADD(Day, -7, getdate()) AND Getdate()
AND Nodes.Device_Type LIKE 'Router'
Group By Nodes.NodeID, Nodes.Caption, Nodes.AvgResponseTime
Having Nodes.AvgResponseTime > 1.10*(AVG(ResponseTime.AvgResponseTime))