To reduce confusion to the users, those two functions, i.e. navigation and input, should be separated. You can have a dropdown with choices in it that moves the user to the desired records when changed, e.g. company name. Set Limit to List = YES because you're just navigating... moving to a record of existing companies. If a NEW record is desired, one of the choices in the dropdown can be "Add New". In that way, Access will navigate to a new record.
Then below in another area of the form, you actually enter/edit the info you navigated to, including a (second) field to enter company name. You can make that second field a dropdown, too, so that people can choose from existing company names; but the second dropdown is not to navigate anywhere, it's just to fill in the company name for that record. Set Limit to List = NO so you can add a totally new company name if needed.
Michigan Dept. of Environmental Quality, Air Quality Division