Getting the weeknumber is not that difficult. (you can use Utils for that)
But searching with that number over dates in the database (that is want you want yes??) That’s another story.
Then you have 2 choices
use a special database function that parse date in the database to the weeknumer and you equal that to the given weeknumber (something like this dateformat(datecolumn,‘w’) = youreweeknr
But this specialized for databases.
the other is as a said before. Generate a between call over a end and a start date (of the week)