Enter data into a cell have comment generated with the current date and time

[soulfriend]

In a worksheet i use cells from B3:B22toG3:G22(bcdef...) but i don't fill all the data in one time.
It is necessary that when i enter the data into a cell, a comment would be generated with the current date and text(text would be nice, but not realy necessary). For example "the customer was registered: 2011.12.05" the date has to remain static.
Is there any way to do it? I tried some things with macros, but i'm starting to give up.

thank you in advance, and sorry for my english.

[snb]

that's a builtin facility in Excel: tracking changes.

[soulfriend]

I found the code that does some of the job,
Sub CommentDateTimeAdd()


Dim strDate As String
Dim cmt As Comment

strDate = "dd-mmm-yy hh:mm:ss"
Set cmt = ActiveCell.Comment

If cmt Is Nothing Then
Set cmt = ActiveCell.AddComment
cmt.Text Text:=Format(Now, strDate) & Chr(10)
Else
cmt.Text Text:=cmt.Text & Chr(10) _
& Format(Now, strDate) & Chr(10)
End If

With cmt.Shape.TextFrame
.Characters.Font.Bold = False
End With

SendKeys "%ie~"

End Sub

and

Private Sub Worksheet_Change(ByVal Target As Range)

If Not Intersect(Target, Range("A2")) Is Nothing Then _

Target.Offset(-1, 0).Value = Now

End Sub

The idea is to combine thees to into one i gues. The first code writes a comment with the date. But i don't know how to make it write a coment in all the cell's i need in multiple colums and only when i write something into cell. And how to leave the date static. ;/