Force user to select suggested entry from Windows Forms Autocomplete ComboBox in VB.Net

Dear Sir,

How to force a user to take a suggested entry into a ComboBox autocomplete in vb.net and can handle keyboard backspace,esc etc?.

so I prefer to use comboxstyle.dropdown because I can do autocomplete typing. so when the user types then the autocomplete appears if the user does on the keyboard backspace and esc then the results are outside the list then the message box appears and I want to not allow the user to leave that combobox until a valid input is entered. Please guide me 

 Thanks