Help with formula to calculate quantity in prior months...

Hello all. I need help. I'm trying to figure out the formula to calculate the following:

If a doctor wants to deliver 300 babies in the month of December, how many office visits will this equate to in the months prior to December, based on the following:

* Most woman present for their first office visit when they are 8-12 weeks pregnant
* Average pregnancy is 40 weeks
* From 8-28 weeks they are seen every 4 weeks
* From 29-35 weeks, they are seen every 2 weeks
* From 36-40 weeks, they are seen every week
* Can use the 1st of the month for calculation purposes

Thank you in advance for the help.

Thank you. What I am really trying to figure out is if a doctor's office is planning on delivering 300 babies on December 1st, based on the criteria I mentioned, how many office visits will he have in November, October, etc. I'm also trying to set this up for the whole year. So if I plug in any delivery number for any month, what visits will occur in those prior months. I'm not even sure if this is doable in excel.

Thanks.

This is great. Sorry, I'm not an advanced excel user. Would you mind explaining this to me, just so I understand how this works. Patients = 300 and this is setup for December only? I'm confused as to how the Week column is setup (i.e. (28), (27), etc.) as well as the stage columns.

Thank you again for your help, this is very helpful.