Thanks for the link, i am following this tutorial,but i have another question, i have done the progem, now there is no error,but i am not getting the expected value of Modified(its a Boolean var)
Code:
var
f: TCalculation;
begin
f := TCalculation.Create(nil);
if f.FNewvalue = True then // the FNewvalue is always zero, which is unexpected
//this will hapen
else
//this
end;