Problem about Ball movement in Wincc

Hai all
I am facing a problem in Wincc. I tried for the ball movement in Wincc. I put a ball in the XY plane of the graphic designer with the position X(100). I need the horizontal movement of the ball. I just want to move the ball to the position X(600). When i script in C action for starting the ball from the X position X(100) it just start from the beginning. I am giving the scripting below.

int a,b;
a=Gettagbit("SW");
b=Gettagword("ball");
if(a==1)
{
b=b+1;
Settagword("ball",b);
}

Please help me....

Does b have to be initialised to 100 before you start to increment???

yes.. I tried that too.. but no use. when i initialize the variable "b" with the value X(100), it doesn't start from that position. first it goes to X(0) and then it moves forward. what is the problem with my script.??