I need someone to fix my excel spreadsheet formulas (ADVANCED WORK)

I need someone to fix my excel spreadsheet formulas. I have a spreadsheet with approximately 120 columns of data. In each column accounts for a 4 week period. We are calculating on 3 periods. (12 weeks) In period 1 We have 100 new loans, In period 2 - 100 New Loans ... Period 120 - 100 New Loans. Every period has 100 new loans. After 3 periods the client's loan is complete and 80% becomes a returning client. Then after another 3 periods 70% return of the original 100 loans. Then after another 3 periods 60% return of the original 100 loans. Then after another 3 periods 50% return of the original 100 loans. Then after another 3 periods 40% return of the original 100 loans. Then after another 3 periods 30% return of the original 100 loans. Then after another 3 periods 20% return of the original 100 loans. Then after another 3 periods 10% return of the original 100 loans. Then after another 3 periods 5% return of the original 100 loans and going forward every 3 periods 5% of the original number remain. WE NEED THIS FIXED WITHIN 24 HOURS.