How to exclude such conditions with Coverpoints?

Hello I’ve the following SV code and trying to do Conditional coverage

 always@(*) begin
      if (a_en && !b_en) 
	op_set = op_a_set;
      else if (!a_en && b_en)
	op_set = op_b_set1;
      else if (a_en && b_en)
	op_set = op_b_set2;
      else
	op_set = no_op;
      
   end // always@ (*)

image

since the If statement will trigger different condition , it would never test the
(a_en &b_en)

how to probably set the cross-Cover point to achieve 100% conditional coverage ?