monte-carlo-simulation - Question and answers

I've been using Excel with @RISK for Monte Carlo simulations on cash flow projections, but when I try to overlay best-case and worst-case scenarios, the results seem inconsistent with my manual risk assessments. I have data on variables like discount rates and sales forecasts, but I'm struggling to define probability distributions that align with the scenarios. Time is tight, so I need a step-by-step approach that's reliable and efficient.