if 20 hours before current time is today,then open file A
if 20 hours before current time is yesterday,then open file B,
use below formula can work
if (NOW ()-TIME(19,59,59)<TODAY (),"Y","N")

but how to change it as excel macro such that "Y" become "open file A" and "N" become "open file B".

Can I use IF ...THEN...to do this?

thx!