Problem with calendar

I have a calendar feature in my worksheet that I use to calculate the weekly averages of our employees. As I change the month, week number, and day of the week the date changes accordingly.
for example, February 2018 1st week, Thursday comes out to 2/1/2018. at the end of the calendar I can place the week as the 5th week and it changes to march 1 and so on depending on the day of the week.
The problem I am having is the first of the month. When I change to February I cant get the first three days to show 1/29/2018 - 1/31/2018. Changing the week of the month to 0 just gives me 1/31/2018 but -1 does not give me 1/30/2018. I am stumped. I might need a whole new calendar design.
I have included an example.