Using cell reference in array formula

I have a set of numbers from B1:B60 and I want to calculate the average of the largest nine numbers. I have set up the following array formula:

=AVERAGE(LARGE(B1:B60,ROW(INDIRECT("1:9"))))

I would like to replace 9 with a cell reference (e.g. A1) so that I can change cell A1 to 6 and calculate the average of the largest six numbers (and so on). Any idea? Thanks.

Thanks! It works.