Math - current cost - cash received if sold

Properties increase by 10% of the original price with each new purchase.

Current Price:

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Properties are built on a required property. If the required property has not been purchased, the Current Price is:

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If I sell this property, the Cash Received:

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However, it's incorrect if the required property is "not owned" in the spreadsheet. I need help figuring out the formula to exclude the price of the required property (the VLOOKUP) for the Cash Received.