Beamer, \framesubtitle

probably is this feature request ... I like to have on each part of frame with allowed breaks common title in different subtitles on each part of frame. something like this:

\frametitle{frame title}
\framesubtitle{first subtitle}
\framesubtitle{second subtitle}

How to achieve this? Beamer put last framesubtitle on each part of frame. Any suggestion is very welcome!

regards, Zarko