weeknum & VBA

Hello hello,

Freshly registered on this forum, I'm here to find a little support with some of Excel functions I'm still not used too.. I'm very new in VBA so please, accept per advance my excuses if I'm not 100% clear with the terminology..

Well.. I got a file from my boss that is linked to an online table. This table contains customer contacts infos such as account number, activation date & time, etc, etc.. (1 contact = 1 line)

Now (for "quick filtering reasons" he said), my boss "needs" to have also in the sheet the week number for every contact we had..(as well as Month & Year)
and as the list grows up everyday with new entries, I thought I could use VBA..
so I wrote a little something that uses the date&time column to have the wanted infos added on every line :

Private Sub Worksheet_change (Target As Range)

Set MyPlage = Range("G2", Range("G65536").End(xlUp))
For Each cell In MyPlage
        
        cell.Offset(0, 9) = "=MONTH(RC[-9])"
        cell.Offset(0, 10) = "=year(RC[-10])"
        cell.Offset(0, 11) = "=weeknum(RC[-11])"
        
       Next
End
End Sub

It works fine with the Month & the year, both return the correct value in the right cells.

But I can't find a way to have it working with the weeknum one.. it returns me a 4 digit value...

For example, with "23.12.2009 09:07" (cell format = custom dd.mm.yyyy hh:mm), the weeknum returns me the value 5740 (when cell format is general, and "01.07.1905 00:00" when in date format) when it should returns me 52!

my only explanation is that it calculates the amount of weeks from 01.01.1900 to 23.12.2009 but yeah... it's not exactly what I need..

Does anyone know how I could solved this issue ? or how I could pass by ?

Thanks in advance for your answer,
I hope you'll understand my question, I'm not that used to write "technical" things in english..

merci merci,
steve