Try this:
// just my example
int i = 0; // static variable
-(IBAction)startAnimation:(id)sender
{
i++;
[UIView animateWithDuration:3.0 animations:^{
if(i%2==1)
tabView.center = CGPointMake(tabView.center.x, tabView.center.y + 60);
else
tabView.center = CGPointMake(tabView.center.x, tabView.center.y - 60);
}];
}