I am struggling to calculate the weekly returns, I need a functioning that will be able to calculate this in excel.

Example

The date is (dd/mm/yy) format and "," is decimal separator. This would be done by using this formula: (Price for last weekday - Price for first weekday)/(Price for first weekday). For example the return for the first week is (2,7391 - 2,7587)/2,7587 = -0,007 and for the second is (2,7619 - 2,7288)/2,7288 = 0,012.

But I am struggling to come up a with a function in excel because I am working with a very big data, so a function will do

Or perhaps if also you can assist with python code to calculate the weekly returns