I have a column called Entry signal that signals a Short Sell Entry but want to implement a backtest with stop loss at 15% that references the most recent last “Entry” from Entry Signal calling (if price rises more than 15% from Entry Price then exit trade, do nothing until next Entry and repeat).

I want to create below Stop Loss column

e.g.

Date       Price    Entry Signal   Stop Loss
2024-01-18  3595.0  NaN            NaN
2024-01-19  3280.0  Entry          NaN
2024-01-22  3505.0  NaN            NaN
2024-01-23  3945.0  NaN            Exit  (since first time price change triggers > +15%)
2024-01-24  4075.0  NaN            NaN
2024-03-07  10270.0 Entry          NaN
2024-03-08  8120.0  NaN            NaN
2024-03-11  14020.0  NaN           Exit

So far I can only think of for looping across each row but there must be a better way given I am working with a dataframe.