Hi, I posted some code a couple of weeks ago based on a Van Tharp blog to calculate position size and stop loss based on the amount of risk you specify:

https://www.prorealcode.com/topic/position-size-variable-to-calculate-per-point/

I used it in my systems for a while but found it difficult to optimise a strategy when both the position size and stop loss can vary.  No doubt Van Tharp has other alternatives and this is just one approach but I went back to having fixed position sizes.  The targets and stop losses are determined by market conditions, bullish, bearish or neither and sometimes depending on the system also on the volatility using the indicator HistoricVolatility.