Try entering =OFFSET($AM$20,1-ROW(),0) in cell A1. When you drag that down,
the ROW() function result increases so that the row of the source cell
decreases.

"Jimmy" wrote:

how do I autofill in the reverse direction?

for example,
cell A1=AM20

I want to drag cell A1 down so that A2=AM19. Currently if I drag down,
A2=AM21.

Thanks,
Jimmy