Variable calculation range

Hi guys,

I'm looking to only calculate the max value between two data points. However, I need to be able to quickly change this (i.e. rather than moving the array manually) - lots of data! I'm just not quite sure how to do this, as an array seems fixed.

I've added a workbook below, with the perfect results (basically I just change N4, O4)

Any questions feel free to ask, ty

Mdn