The Dink Network

Make the rock "not hard" in the editor, then

sp_hard(&current_sprite, 0);
draw_hard_sprite(&current_sprite);

after sp_x() has been changed.

Instead of using &stonem (which I assume is a global), you might want to learn the editor_seq/editor_frame trick, unless the state of the rock matters in other scripts, of course

LATE ADDITION:

void main( void )
{
//that opened main()
sp_speed(&current_sprite, 1);
int &mydir;

if(&stonem == 1)
{
//that opened the if()
sp_x(&current_sprite, 344);
}
//that closed the if()
}
//that closed main()

You might want to check the brackets also.