Change pravalli’s snippet froim DayOfWeek.Sunday to DayOfWeek.Monday
If today is Monday, substract 3 days, else substract 1 day.
Note that this is still an incomplete expression since you also need to correct input data Sunday -2 days. So you need to nest 2 if-then statements in each other if you really want to do it in 1 expression.
And even then you still need to compensate for national holidays.
My advice: don’t try and solve it in one expression but make it a wee bit more robust, and then export it as either a separate workflow of even library activity.