Oh wow, my first job in the industry was building something very much like this! It was actually quite powerful: the UI and simulation were done by Microsoft P

Oh wow, my first job in the industry was building something very much like this! It was actually quite powerful: the UI and simulation were done by Microsoft Project (https://www.microsoft.com/en-us/microsoft-365/project/project-management-software https://www.microsoft.com/en-us/microsoft-365/project/projec...), which I would describe as "the Excel of project management" in that it was an ENORMOUS bag of features for building Gantt charts. The coolest part was that it integrated with Outlook's calendar, so if a task started on June 1st, was assigned to Bob, took two weeks, and Bob was on vacation from June 8th-22nd, it calculated the end date for the task as the end of June. The Monte Carlo part was run by Crystal Ball (which was a startup then, but has since been acquired by Oracle). It was a mature tool, so there was a big library of probability distributions (https://docs.oracle.com/cd/E57185_01/CYBUG/define_assumption_dialog.htm https://docs.oracle.com/cd/E57185_01/CYBUG/define_assumption...), you could enter correlations (if X task takes a long time, Y is going to take a long time too), and you could analyze the output in all sorts of ways (how sensitive is the deadline to this task, how frequently is this task on the critical path, etc.). The implementation was quite a hack - a hidden instance of Excel running Crystal Ball and lots and lots of VBA to manage everything. I'm not sure that it was ever used for real :(