any other extra batsman play in place of smith

No. ICC cricket rule does not allow this.

No. If Graeme Smith is not batting, then no one else can bat in his place.

What do you mean by extra batsman? Its well known that a substitute can only field for someone injured. He cannot bat or bowl for the team inplace of a regular member of the team.

So, basically South Africa have 8 wickets remaining tomorrow to get the runs or salvage a draw. Smith wont bat unless maybe 5 runs are required.

At this stage, a batsman cannot get replacement! Smith may have to come back to the crease, if required! It should be interesting to see the progress tomorrow!

no one

Not in this test
Prince might be in the one day team or another batman

No.
A team cannot be altered after the start of the game. And the 12th man can not bat, bowl or keep wicket. He can only field.
Which is unfortunate for South Africa.

l guess bowlers can bowl extras and add to the score of smith.. that way extras can play insted of smith.. and that is quiet official.

No, the rule will not allow

wheres ashwel prince

No, only subs allowed are fielders.

Subs are not allowed in Test Cricket. If a player gets injured then the fielding side can not replace him no matter what injury has occured. Even if a team gets 6 places injured then no replacements can be made.

If you mean who will replace him in the OD l side, then Herschelle Gibbs will more than likely replace him, with Jacques Kallis moving up in the order.

Without smith south africa can win or draw the test match because they still have good batsman and allrounders in team.

One man does not a Team make.

read this about substitution
http://theage.com.au/news/Sport/Cricket-substitution/2004/12/31/1104344986451.html

Look at poor Rick McCosker - Smith has it easy - Rick came out of Hospital with a broken jaw to bat in his second innings.