The Dink Network

I want to spawn a sprite from small (5%) , then grow it large. But it disapears when it reaches its size.
int &felmx = sp_x(&current_sprite,-1);
int &felmy = sp_y(&current_sprite,-1);
int &felm = create_sprite(&felmx,&felmy,6,971,1);
sp_size(&felm,5);
sp_brain_parm(&felm, 400);
sp_brain(&felm, 12);
wait(3000);
sp_brain(&felm,6);
sp_speed(&felm,1);
sp_target(&felm,1);
sp_base_walk(&felm,970);