[Cbc] Constraint to make a solution infeasible

[Terry]

CBC will find an optimal solution to my IP problem. Now I want the "next" optimal solution. That is, I want to make the previous solution infeasible and run CBC again to find another solution.  

Here's an example I'm working with:

Minimize
 x1 + x2 + x3 + x4
Subject To
 5 x1 +  5 x2 >= 10
 7 x3 + 14 x4 >= 21
Integers
 x1
 x2
 x3
 x4
End


Optimal - objective value 4.00000000
      0 x1                     2                      1
      1 x2                     0                      1
      2 x3                     1                      1
      3 x4                     1                      1


Can I add a constraint so that [2 0 1 1] is infeasible, but allows any other answer? I'm afraid this is a stupid question, but I don't see how to do it. 

Thanks.
Terry