The substitution behavior of some alloying elements in CoZr is investigated using the discrete variational Xa cluster method. The method proposed by the author to predict the substitution behavior is amended to consider the local lattice relaxation. A diagram is drawn based on the binding energies of clusters with alloying elements taking either Co or Zr site. Two straight lines on the diagram separate the alloying elements into three groups with different substitution behavior. The elements above the upper line will take Zr sites and those below the lower line will take Co sites regardless of the composition. The substitution behavior of elements in between the two lines will be affected by the alloy composition. The concept of site competition and step ordering is proposed.