Cascading Drop Down Lists in SharePoint

There are a couple of suggestions on the SharePoint Uservoice site for cascading lookup lists. Unfortunately one of them has 60 votes and Microsoft don't generally look at ideas under 100 votes.

https://sharepoint.uservoice.com/forums/329214-sites-and-collaboration/suggestions/7140453-i-hope-cascaded-lookup-column-and-chart-webpart-in

I am trying to make this process work for me in Sharepoint.

I have a main  list called  registration. 

I also have 3 lists called Employee, Courses and Categories.

Course List has columns: Course, category, Course ID, Date, etc

Categories List has one columns, category

Employees Field has Fields : Department, Employee ID, Employee Name etc

From the Registration List, when I Select a category, In the drop down I only want to select a course, on the courseID field

When I Select  a   Department,  from the Employee List, I only want to see Employees in that department in the Employee ID field

When I Select a course, I only want to choose dates for that course  

I have seen the codes above, but I am having a hard time making it to work.

Any help will be greatly appreciated.