Ok sorry!! Didn't mean to make things more confusing!! I will break it down:

**Summary**
Think of the data I gave you in Column B as the increasing fatness of my dog each year, expressed as a percentage.

**Step 1**
The raw input data in Column B is expressed in a form like 0.10. The only reason I have the data as 0.10 is because I need it to show as 10%.

**Step 2**
The next step is to calculate the cumulative percentage, to show the overall change in my dog's fatness: I cannot multiply the raw data together as it is (i.e. 0.10 * 0.20) because it would give a very small and wrong answer. Therefore, each percentage must have + 1 added to it to be workable.

**Step 3**
Now, for the first two years, the cumulative, or overall percentage change in my dog's fatness would be 1.1 * 1.2 = 1.32 or 132%. I don't want it to show as this, because it would seem that my dog has balooned. So, I minus 1 from the final answer, giving a much more presentable 0.32 or 32%.

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I hope that explains my example.

**My problem**
In excel, if I try to drag the formula down and let it repeat itself through all the values, it will not do so successfully - it seems to always miss a cell out. Try to drag E3 down and you will find that it will miss (B2 + 1) * from its calculation. This problem occurs every time, and the only solution is to manually type the missing cell in - exhausting if you have a large amount of data!

**Possible solution?**
I think a custom formula that

*adds one to each value before multiplying* would enable me to drag E3 down without any problems.

**Conclusion**
I need a way to multiply raw percentage values together (e.g. 0.10), a bit like PRODUCT does, but

*very importantly* it must add 1 to each value first. As explained above, this is a necessity. I can then minus 1 to the end result by myself.

If you have read through all this you are a hero!! Sorry if it is a bit long - hope you understand what I'm trying to do now.