Altering a calculation based upon variable values from a drop down list

Hi All,

I have another problem - Basically I have a workbook with various tabs for recording referrals and placements and I would like to have a formula calculate the end date and two review dates for a client once their start date has been agreed. I have the sheet working for when the placement is 8 weeks long, however I am stuck on how to get the formula to change if a different parameter is selected in column F. I have tried altering the formula in cell C5, however this is incorrect but gives an idea of what I am trying to achieve. The review dates for a 5 week course would be due the start of week 3 and then start of week 5.

I want to simply put their start date into column B and then have the formula populate columns C, G and H.

I have attached an example sheet to assist with my request.

Many thanks in advance for this.

Cheers