How to get TField.oldvalue ONvalidate event???

[halenpolen]

Hi, I Have a problem ,How to get TField.oldvalue ONvalidate event???
this my code:
uniquery1no.onvalidate:=uniquery1noValidate;
procedure TForm1.uniquery1noValidate(Sender: TField);
begin
sender.oldvalue;//this is the problem,sender.oldvalue=sender.newvalue
sender.newvalue;
end;

Thx for ur help

[bork]

Hello

You should read attentively the section of the Delphi help about the OldValue property of the TField component:

Note: the OldValue property is only usable when data is accessed using the TClientDataSet component or cached updates is enabled.