Vlookup or VBA to get correct week No for Month

Hi All,
Need some help here.

I have on Sheet1 Column A the Financial Month. In a month, there are 4 or 5 weeks and I want to get the start day of every week (Monday) as seen in sheet2
Instead I managed only to get the last week day that applies all weeks of the month. (instead of every week)

Is there a way to get the desired output via formula or script?

Regards,
Nironto