Actually, in one cell, you should use vba/macro to "paste special" the value of the first cell (where the date was first got as the current date).
Code:
'
Range("A1").Select
Selection.Copy
Range("A3").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Range("A1").Select
Application.CutCopyMode = False
Selection.Copy
Range("A3").Select
Selection.PasteSpecial Paste:=xlPasteFormats, Operation:=xlNone, _
SkipBlanks:=False, Transpose:=False
In the example, cell A1 contains the "now" value with format "dd/mm/yyyy hh:mm:ss" and cell A3 the stored value for later use.