Transition to block

[jaspreet]

Hi,
I want to ask that how to apply transitions to only a block or a box
with in a frame but not to the whole frame?

If I tried following, transition effect applies to whole frame
=======================================
\begin{frame}
\begin{block}{}
\transdissolve
\centering History of \LaTeX{}
\end{block}
\pause
\begin{bclogo}[couleur = green!30,arrondi = 0.1,
logo = \bccrayon, ombre = true]{Bclogo seems to be the most
versatile!}
This box is made with bclogo. Corners are rounded and I love that
crayon :-).
\end{bclogo}
\pause
\shadowbox{This is a shadowbox.}
\end{frame}
===================================

I know this is very silly question but I don't know it :) Please help
me .

Thanks