one way:

B1: =IF($A$1=ROW(), "X","")

Copy down to B31.


In article ,
"Ed" wrote:

In Cells A1, I am entering the day of the month.

Depending on the value of A1, I want it to mark an X on one of cells B1 to
B31.

e.g. if A1 is the 20th day of the month, I want it to automatically mark
cell B20 with an X.

How do I do that?

Thanks.