Function Chuanhoachuoi(str As String) As String
    Dim sChuoi As String
    Dim mlen As Long
    Dim i As Long
    'Neu chuoi =0 thi khong xu ly
    If Len(str) = 0 Then Exit Function
    'Xoa bo cac ky tu trang o dau va cuoi
    str = Trim(str)
    'Dem so ky tu chuoi
    mlen = Len(str)

    'Loai bo hai ki tu trong lien tiep
    For i = 1 To mlen
        If Mid(str, i, 1) = " " And Mid(str, i + 1, 1) = " " Then
            str = Replace(str, "  ", " ")
            i = i - 1
        End If
    Next

     For i = 1 To mlen
        ' Chuyen cac ky tu dau tien mot tu sang chu hoa
        If Mid(str, i, 1) = " " Then
            sChuoi = sChuoi & " " & UCase(Mid(str, i + 1, 1))
            i = i + 1
        Else
            'Chuyen chu cai dau tien cua cau sang chu hoa
            If i = 1 Then
                sChuoi = UCase(Mid(str, 1, 1))
            Else
                sChuoi = sChuoi & LCase(Mid(str, i, 1))
            End If
        End If
     Next
    Chuanhoachuoi = sChuoi
End Function

Private Sub Worksheet_Change(ByVal Target As Range)
     Dim str As String
     If Not (Intersect(Target, Range("$F:$F")) Is Nothing) Then
str = Chuanhoachuoi(Target.Value)
Target = str
     End If
End Sub