Add an entrance animation to your graph (wipe works well with bar charts)
then select effect options from the drop down list next to the animation. Go
to the chart effects tab and select how you want it to come in (eg as one or
by series). Play until you get what you want
You can do more complex things by ungrouping the chart and animating the
elements separately - depends what you're after.
Henry,
It all depends on the animation effect you apply to the graph, depending on
the animation you can just animate the graph as a whole or animate in series
and such. So try it out, appear for instance will have them all.