Code to check ComboBox.Value doesn't already exist in range before attempting to delete

Im using the following code to delete usernames from a sheet, and consequently from a dynamic range. The code worked fine but Im trying to add some code that checks to make sure the username entered in the combo box Username is present in the dynamic range Usernames. If it is not present then it displays a message informing the user that the username does not exist.
I am currently getting runtime error 13 Type mismatch on the third line: If Username.Value = Rng Then

Private Sub CommandButton4_Click()
Set Rng = Worksheets("Users").Range("Usernames")
    If Username.Value = Rng Then
        Msg = "Are you sure you want to delete the username: " & Username.Value & "?"
        Ans = MsgBox(Msg, vbQuestion + vbYesNo)
        Select Case Ans
            Case vbYes
                Dim c As Range
                With Me.Username.Value
                Set c = Worksheets("Users").Range("Usernames").Find(Me.Username.Value, , xlValues, xlWhole, xlByRows, xlNext, True, False, False)
                If Not c Is Nothing Then
                c.EntireRow.Delete
                    Me.Username.Value = Sheets("Users").Range("G1").Value
                    With Worksheets("Users")
                    Username.List() = .Range("Usernames").Value
                    End With
                End If
                End With
                Exit Sub
            Case vbNo
                Exit Sub
          End Select
    Else
    MsgBox "Username does not exits. Please selet a user to delete from the Username dropdown list."
    End If
End Sub

Thanks,
James