Creating formula based on if data is correct in cell

Hi everyone- I'm having a problem with a formula for work. Attached is a simplified version of my problem.

My job is to find the %s of all insured cars, based on two different types of insurance. However, one insurance (type A) runs out before the other, and when that happens we use a forecasted/projected amount. I created a simple IF formula to show the insured % amounts for the next three months. If theres a value in type A insurance, use total insured cars/total cars. If there isn't a value in Type A, use total insured cars/total cars + forecast A. This formula breaks down in the months of Sept and Oct (if you look at the comments in the attached wrkbook).


Thanks for any and all help!

xpost - http://www.excelguru.ca/forums/showt...orrect-in-cell