Large data, time series data analysis

Hi, any help will be appreciated! Thanks in advance.

Book1.xlsx

I'm trying to calculate returns from start to end. Start is a given point. And end is either Target or Stop point. If target comes first then target/start-1 but if end comes first then end/start-1.

Data has time stamps and the appropriate points for that time. How can I create a logic that can handle 5000+ rows of data and run the same logic for a given day? Please see attachment for details.

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Or is this something not even possible in Excel? Any other suggestions for free programs would be greatly appreciated.