Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address Like "$*$*[!:]" Then
    Dim i As Integer, str As String
    str = vbNullString
    On Error Resume Next
        str = CStr(Target.Value)
    On Error GoTo  0 
    If str = vbNullString Then Exit Sub
    i =  1 
    Do While i <= Len(str)
        If Not (Mid(str, i,  1 ) Like "[A-z]") Then
            i =  0 : Exit Do
        End If
        i = i +  1 
    Loop
    If i <>  0  Then MsgBox "Присутствует символ не латиницы."
End If
End Sub