Correct way to formulate a percentage on stock for stop loss price

I am making a spreadsheet where I enter the current value for individual stocks each day. I am able to calculate the profit or loss of each stock but want to have a calculation where this price less 15% gives me a quick dollar amount to enter as a stop loss in my portfolio.
Thank you.

Hello,

(if I do not completely misunderstand your questions):

Price-15% = Price - Price * 15% = Price * (1 - 15%) = Price * (1 - 0.15) = Price * 0.85 ( where Price-15% is your Stop Loss price)

In other words
If the (paid) price is in A1 and your stop loss price should be in B1 - put: =A1*0.85 into cell B1.

Shoot, I left out what I didn’t know how to do. I figured correctly and you confirmed the percentage on a stock that’s showing a profit. How would I enter the formula if the price is in the red. Obviously I don’t want to use that price in my calculation would I?
Thanks

I absolutely don 't understand what you mean by your comment.