No chance I'm afraid, unless you have paid full fare economy and have a top level frequent flyer card and a great deal of luck.
(Though the time I was upgraded I a) had a top level card, b) hadn't asked for it and c) was flying on an award ticket!)
Other than that, you'll find most check-in staff and CC will have higher respect for a paedophile than someone fishing for an upgrade.
Well, maybe not, but this is one of the many "do not ask" questions on PPRuNe!