Auto Stop loss calculation using editable RPT value

Our journal should be able to calculate automatic stop loss value of the trade if we make RPT ( risk per trade ) filed in the journal Editable. Like for example I buy 100 stocks of a company at the price of 250 and lets say my risk per trade is 10% i.e. 2500. If we make RPT filed editable and I type 2500 (stop loss value) in that field, it should automatically set 225 as my stop loss.