Formula for a reaction when another column hits a certain value.

Hi, I was wondering if there is such a thing as a formula that adds a value to it's own cell when the cell adjacent to it has reached a certain value.

My best example of this would be: I buy one shop, however I spend the profit from this shop to buy another shop, and so on. In one column I would have the amount of shops I own and in the next the profit, when the profit hit $50,000 it would automatically make the number of shops owned cell adjacent to it go up by one.

Thanks

P.S. I don't own or plan on owning any shops