I'm not entire sure what you are trying to achieve, but there is a logical error in your if statement:

If newClosestToAudience is 2 then you are essentially asking if 2=3 or 2=1.  This will always resolve to false whatever the value of newClosestToAudience.

It would probably help to see the whole method to understand how you are trying to achieve this as this snip doesn't give much context.

Think step-by-step about what you've written: first you set x = y and then ask if x == x + 1 or x == x - 1.  Clearly x is never going to be equal to x + 1.  I think what you actually want is something along the lines of:

1. if (newClosestToAudience != closestToAudience) {
2.       doSomething();
3. }
4. closestToAudience = newClosestToAudience;
   

You might need to post some more of your code then.  Are you sure that newClosestToAudience is actually being set correctly?

1. int closestToAudience;
3. public void setClosestToAudience(int value)
4. {
5.       closestToAudience = value;
6.       println("Do Something!");
7. }

ok so closestToAudience is determined by using the below code in conjunction with another function, to decide which vector point out of 5 is closest to the mouse - 

What you've got there looks reasonable so I'm pretty sure the problem is elsewhere in your code.  Is the problem still that you're not getting an event when closestToAudience changes or is it something else?  I suggest you get what you've got working without the OSC messaging first and then figure that out afterwards.  For comparison this code does what you want in a simple case:

1. BallCollection balls;
2. ball closestToAudience;
3. bool ballchanged;
5. void draw()
6. {
7.       ballchanged = false;
8.       for each ball b in balls
9.       {
10.             if b.distanceToAudience < closestToAudience.distanceToAudience
11.             {
12.                   setClosestToAudience( b);
13.             }
14.       }
16.       if ballChanged
17.       {
18.             //Do whatever you need to do?
19.             //Can a ball control it's own 'bang'?
20.             closestToAudience.bang();
21.       }
22. }
24. private void setClosestToAudience(ball b)
25. {
26.       closestToAudience = b;
27.       ballchanged = true;
28. }