Formula for Week number within a fiscal month

Hello All, I am hoping that someone could help me out with a formula.

Currently I have a formula that displays the fiscal month for my job. The months are as follows: Jan = 12/22 - 1/21 Feb = 1/22 - 2/21 and so on.

=IF(C2="","",TEXT(DATE(YEAR(C2-21),MONTH(C2-21)+1,1),"mmm"))

I am trying to create a formula that will display the week number of the fiscal month (above). I am a bit confused on how. Any help is appreciated.

Thanks!