In column `A`

I have a set of numbers (over 1,000), and I want to get an average of a block of them at a time, (e.g., 10, so `A1:A10`

then `A11:A20`

and so on) and write these averages into column `B`

, such that `B1`

contains the average of the first block, `B2`

the second block and so on.

Then, in `C1`

I would like to have a value which defines the number of rows each average should consider (e.g., 10 = `A1:A10`

,`A11:A20`

... and 25 = `A1:A25`

,`A26:A50`

... and so on).

When I change the value of `C1`

I want column `B`

to update automatically to average using the new block sizes.

How should I go about doing this?