Basic Matlab Simulink Project - Convert a small spreadsheet model into Simulink

I have a simple worksheet which i would like converted into Matlab Simulink. The worksheet calculates a series of positives and negatives and determines the net balance. Based on the historic numbers in the spreadsheet, i would like the forecast numbers to be stress tested stochastically within simulink (i.e. look at historic trends and make stochastic assumption about what values will be in the future). I would like to be able to easily adjust these forecast assumptions within the Simulink model once it is built.