As long as you create the alert on a chart that is both time-based and has an interval that is a factor of 4 minutes, you should easily be able to do this with an alert. Just compare the price at “now” vs the price x bars ago +/- an offset of 500 points. If you need it on a non time-based chart type (renko, range, etc..), an interval greater than 4 minutes, or an interval that is not a factor of 4 minutes you’ll probably need to go the indicator/strategy route.