The data are in one column with variable number of rows. How can I write a
macro to calculate average from every two or three consecutive rows?

For example, see the following conversion:

Data Average every 2 rows average every 3 rows
1 2 3
3 6 9
5 10 15
7 14 21
9 18
11 22
13
15
17
19
21
23

Thank you very much for your time.