I need to get the week number in excell from a cell with a date (dd/mm/aaaa),
but the first week of the year has 3 possiblilities, first week, with day
nº 1, first week with at least 4 days of the new year or finally the first
full week.

How to do this in excell ? I tried with weeknum() but I can't choose the
first week

Thanks.