Alternative way to replace Fast Shutter

I just bought a Canon S2 IS. When I still use Canon A95, there's a fast

shutter and slow shutter mode at the mode dial, that two mode is not
exist at Canon S2 IS.


Is there any other mode which I can use on Canon S2 IS to replace that?

I can set it manually to have fast shutter, but that need some time to
adjust it.
It's just in case, I was in a car, bus, or train, I saw a nice object
and wish to take a shot on it, I have no time to adjust it, last time
when I use Canon A95, I use to switch to Fast Shutter mode and shot it.

But now I have to figure out a way to do that.


Anyone have any idea on that?


Peter CCH