Non-Printing Characters: Box with a Question Mark Unable to remove

[rlv]

Another approach is instead of trying to exclude characters you don't want, is to instead only include the character you do want. Phone numbers lend themselves well to this.

Function CleanContactNumber(ContactNumber, LegalCharacters As String) As String
    Dim Ch As String, CleanNumber As String
    Dim NumStr As String
    Dim I As Long

    NumStr = CStr(ContactNumber)
    CleanNumber = ""
    For I = 1 To Len(NumStr)
        Ch = Mid(NumStr, I, 1)
        If InStr(LegalCharacters, Ch) Then
            CleanNumber = CleanNumber & Ch
        End If
    Next I
    CleanContactNumber = CleanNumber
End Function

So the cell formula would be

=CleanContactNumber(C11,"0123456789-")

Where "0123456789-" are the legal characters.