pass note to parenthesis in author(year) in-text citation

Question

I was wondering whether it is possible to pass a note to the parenthesis in the \cite command. I am using bitex and the natbib package and am looking to produce this:

Miller (1990, Figure 12)

\cite[][Figure 12]{Miller1990} produces the same as \citep would: (Miller, 1990, Figure 12)

I was hoping that I could create a new command along the lines of:

\def\citecomment#1{\citeauthor{#1} (\citeyear{#1}, \note)}

and where \citecomment[][Figure 12]{Miller1990} would produce the desired result, but I don't know what argument calls the note (\note is obviously not the correct one).

See the MWE below:

\documentclass[10pt,a4paper]{article}
\usepackage[]{graphicx}
\usepackage[]{color}
\usepackage[a4paper, vmargin={40mm,40mm}, hmargin={40mm,30mm}]{geometry}
\usepackage{subfig}
\usepackage{floatrow}
\usepackage{alltt}
\usepackage{amsmath, amssymb, amsthm, arydshln, array, booktabs, here, lineno, latexsym, multirow, epsfig, pbox}
\usepackage[format=hang,font=normal, labelfont=bf, textfont=normal]{caption}
\usepackage{url}
\usepackage{pdflscape}
\usepackage[round]{natbib}
\usepackage[doublespacing]{setspace}
\usepackage{fancyhdr}
\usepackage{hyperref}
\usepackage{paralist}

\def\citeapos#1{\citeauthor{#1}'s (\citeyear{#1})} % This creates a command for citations with apostrophes.
\def\citeay#1{\citeauthor{#1}, \citeyear{#1}} % This creates a command for Author, year.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\pagestyle{plain}
\begin{document}

This approach has been used by \cite[][Figure 12]{SaezZucman2016QJE}.\\
This produces the same result as \citep[][Figure 12]{SaezZucman2016QJE}.\\
But I want a citation that says Saez and Zucman (2016, Figure 12) did this or that.

\bibliographystyle{aer.bst}
\bibliography{/Users/isabel/PhD/Dropbox/myreferences.bib}       

\end{document}