Adding Text Entered In Userform Combobox Into Dropdown List

I am not sure if this can be done easily but essentially what I have is a userform that fills out a form that will used by several different people and saved to a central location.

There is a blank combobox currently labeled "Supplier:" that each person fills out each time on the userform (there are no dropdowns yet).

What I am wanting to do is for every person who saves (I have coded the save button) with the "Supplier:" combobox filled out to save what they entered and input that into the combobox dropdown so when the next person uses the userform the entry the previous person entered would be in the combobox as an option to select.

Essentially, a combobox populates itself based on what previous users have entered into it.