UPDATE [tablo] SET [alan] = SOYISIM_BUYUK([alan])

SELECT SOYISIM_BUYUK([alan]) FROM [tablo]

Function SOYISIM_BUYUK(arg As String)
Dim liste As Variant, b As Integer
 
liste = Split(arg, " ")
 
For b = 0 To UBound(liste)
    liste(b) = LTrim$(liste(b))
    If b = 0 Then
        liste(b) = BuyukHarf(Left$(liste(b), 1)) & KucukHarf(Mid$(liste(b), 2, Len(liste(b))))
    Else
        liste(b) = BuyukHarf(Left$(liste(b), 1)) & BuyukHarf(Mid$(liste(b), 2, Len(liste(b))))
    End If
Next
 
SOYISIM_BUYUK = Join(liste, " ")
End Function
 
Function BuyukHarf(arg As String) As String
    BuyukHarf = UCase$(Replace(Replace(arg, "i", "İ"), "ı", "I"))
End Function
 
Function KucukHarf(arg As String) As String
    KucukHarf = LCase(Replace(Replace(arg, "İ", "i"), "I", "ı"))
End Function