=ENT(MOD(ENT((A2-2)/7)+3/5;52+5/28))+1
Sub Test_Formule()
Range("B2:B5002").Formula = "=INT(MOD(INT((RC[-1]-2)/7)+3/5,52+5/28))+1"
End Sub
Sub Test_Code()
Dim X%
Application.ScreenUpdating = 0
For X = 2 To 5002
Range("B" & X) = DatePart("WW", Range("A" & X), vbMonday, vbFirstFourDays)
Next
End Sub
DatePart("WW", Range("A" & X), vbMonday, vbFirstFourDays)