Stop Loss Formulas for Stock Trading

Is there any one out here that thinks they can help me with a formula for
finding a stop price for a stock? I have found an indicator for buying and
selling stocks. Now I just want to write a stop loss somehow so I can limit
my downside. My signals for Buy and Sell are pretty simple. In my
spreadsheet I have the date, open, high, low, and close. Off of those
records I used a =if(and( )) statement to determine my buy and sell points.
I wrote them like this =if(and(a3<a2), "buy", " ")and the same for the sell
side. SO then next to my open, high, low, close I have a column that is a
buy column and one that is a sell column. NOw when I get a buy I would like
to write something like this =when(e4=buy, find the value of the close that
period and had say x factor to it for the stop, if the high reaches that
point the exit the trade. Same for the sell side. DOes anybody have some
tips or suggestions. I been working on this for close to 10 hours now and I
haven't gotten anywhere. I am new to excel so would appreciate any help.
Thank you

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