Looking to make multiple selections in a userform

I am working on some code that will pull information from a daily file and will sort it based on user selections. These selections will be for the area supervisor and the machine numbers associated to that person. I intended to use a checkbox however I need to make multiple selections (some users will only want to see their machines under their supervisor). I have searched all morning and have not found anything that points me in the right direction.

Any help will be greatly appreciated, thank you