Column Formula (Range Selection)

[#1]

I have a column of data sequenced in time, most recent result at the top of the table. I want the top row value of a new column to be evaluated (Maximum minus the Minimum) at that most recent time  and a fixed # proceeding values (say the previous 14).

So each new value at each time will be the peak-to-peak variation of 15 results; the previous 14 results the one at the current time.

If was in Excel I could drag the mouse to select a range of cells to evaluate the difference of Min&Max over the range...

[#2]

If I am correctly interpreting your question, here is one possible way to handle it as a formula for a new column

If( Row() <= 14,
	bottom = 1,
	bottom = Row() - 14
);
Max( :weight[Index( bottom, Row() )] ) - Min( :weight[Index( bottom, Row() )] );