for example, I have two excel files, excel1 and excel2.

In excel2, I have written some functions, like it takes the values from
column A, multiply it with 2, and save the results on column B. Too
simple?

In excel1, I give the values to column A of excel2, my purpose is to
read the corresponding cells in column B, so that I can get the
calculated results. (excel2 should not be opened)

how to write this excel1 with VBA?