I've found on the net a useful trick that does exactly what the title says. This is the code:
\newcommand{\mymarginpar}[1]{%
\vadjust{\smash{\llap{\parbox[t]{\marginparwidth}{#1}\kern\marginparsep}}}}
It works fine, the only problem is that the note is created in the left margin. Is it possible to put it in the right margin instead?
\reversemarginparcould be your friend. – Count Zero Jul 14 '13 at 18:41