I hope that my question is not too dopey since it is my first post here and I would like to avoid to embarrass myself

I would like to change in my talk with Beamer-class the frame-numbering to a page-numbering -- which I managed. I suppose it is not the most elegant solution since I changed to complete footer definition from my favorite theme (CambridgeUS). The missing thing is now that I do not know how to get the total number of pages:
Code: Select all
\defbeamertemplate*{footline}{infolines theme}
{
\leavevmode%
...
\insertpagenumber{} / \WHATISTHETOTALPAGENUMBER \hspace*{2ex}
% \insertframenumber{} / \inserttotalframenumber\hspace*{2ex}
\end{beamercolorbox}}%
\vskip0pt%
}

If possible I am looking for a 'total page number' without counting the appendix/backup-slides. Currently I am masking appendix-slides using the appendixnumberbeamer style-file -- but I guess that I have to rewrite appendixnumberbeamer.sty anyway to use page numbers instead of frame numbers as well...
Cheers & Thanks for any ideas,
Thomas