mathematical optimization - Integer Programming unequal constraint -

I am trying to model the following barrier in MIP:

  x_1 + X_2 + ... + x_n! = D   
 The idea is to apply the variable J1, if x_1 + x_2 + ... + x_n = d and to add constraint  
  z   
 But how can I prepare the barrier  
  (x_1 + x_2 + ... + x_n = D) ==> ; Z = 1   
 In an integer program.   
 
 
 I think all  x_i  are integers  l  And  you  give such a constant value  
  l   
 and  y  A binary variable, these constraints express what you are looking for:  
  x_1 + X_2 + ... + x_n & gt; = D + 1 + (LD-1) Y x_1 + x_2 + ... + x_n & lt; = D-1 + (Ud + 1) (1-y)   
 If  y = 0  then the first forced  x_1 + x_2 + ... + X_n & gt; = D + 1  and second bound  x_1 + x_2 + ... + x_n & lt; = U  is satisfied with the definition of  U .  
 If  y = 1  then the second forced  x_1 + x_2 + ... + x_n & lt; = D-1  should be held and the first bound is  x_1 + x_2 + ... + x_n & gt; = L   L  is satisfied with the definition.  
 (Please check the typo.)  
 
 This integer programming has a  notorious big M method  and may be worse off. Bad situation can occur.  
 
 For further tips, look for Google's "Integer Programming Tricks", especially for this big M method move.