{ ... }
type
 PYourMethod = ^TYourMethod;
 TYourMethod = procedure(S: string) of object;

procedure TMainForm.Button1Click(Sender: TObject);
begin
 ExecMethodByName('SomeMethod');
end;

procedure TMainForm.ExecMethodByName(AName: string);
var
 PAddr: PYourMethod;
 M: TMethod;
begin
 PAddr := MethodAddress(AName);
 if PAddr <> nil then
 begin
 M.Code := PAddr;
 M.Data := Self;
 TYourMethod(M)('hello');
 end;
end;

procedure TMainForm.SomeMethod(S: string);
begin
 ShowMessage(S);
end;