using MAX formula for user-defined number of cells

I have a row of 10 numbers from cells A1:A10. I want to use the MAX function to find the largest value but I want to base it on a user-defined number of cells. The numbers of cells to use is always going to start from the right (cell A10).

As an example, data is a follows:

A1 = 50
A2 = 100
A3 = 900
A4 = 10
A5 = 40
A6 = 500
A7 = 20
A8 = 90
A9 = 300
A10 = 200

If the user wants to use 5 cells, then the max is 500 (finding the MAX in A6:A10). If the user wants to use 3 cells, then the max is 300 (finding MAX in A8:A10). And so on. Thanks in advance for any comments.

Assuming:

1) the user is entering the number of cells to use in cell D1
2) numbrer of cells always refers to "the last X number of cells"

...then use this formula:

=MAX(INDEX(A1:A10, 11-D1):A10)