Calculate compounding "interest"

Not really compounding interest, but sort of. Here's what I need in layman's terms. Hopefully someone will understand this logic.

In the attachment, I need to calculate "Est. Purchase" for the number of "value in B1" purchases of each item in Column A for Rows 4 through 30 where "Value in A" <> "". Each time a purchase of Row A (let's stick with A4) is made, the value of the item increases ~15%, so the second item of A4 will be ("value of B4" * 1.15), the third will be (("value of B4" * 1.15) * 1.15), and so on. I need to calculate the total purchase price of "value in B1" items of A4.

So if B1=3, I need C4 to be ("value of B4" + ("value of B4" * 1.15) + (("value of B4" * 1.15) * 1.15)), and then I need that repeated for all rows where "Value in A" <> "". The value in B1 will be changed by the user in order to determine which item in Column A has the highest return value of other calculations that I left out of the attachment (they are irrelevant to this problem), so it will be anywhere from 2 to 20 (or even greater).

I wouldn't write a code for this. Just realize that (((B8*1.15)*1.15)*1.15) is the same as( B8*(1.15^3)). I would just have your formula in column C reference $B$1. so your formula in C would look like =IF(A10<>"",B10*(1.15^($B$1),"") and just autopopulate it on down. A10 and B10 should change to A11 and B11, respectively with your "compounding" remaining the same. Hope this helps

That's not exactly right. The end result is B4*(1.15^($B$1)), or where B1=5, that calculation would be B4+(B4*1.15^5), or just two numbers being added. What I need is B4+(B4*1.15)+((B4*1.15)*1.15)+(((B4*1.15)*1.15)*1.15)+((((B4*1.15)*1.15)*1.15)*1.15)+(((((B4*1.15)*1.15)*1.15)*1.15)*1.15), or a total of 5 numbers being added together. It is all the subsequent additions that I can't seem to calculate properly.