Forced LE instantiation

Hi. If I add two vectors on my CyII, I get a chain of LE in arith mode, containing two 3-input LUTs each. But, I don't want an adder, I want the same routing, but different equations within the LUTs. I have tried the CARRY_SUM instantiation, and I have tried to assign the equations to the cells. It worked perfectly well when I implemented a FA chain this way, but when I try my own equations, quartus split the operation into one LE for the sum and one for the carry equation.

Example of the N:th instantiation:

instN : CARRY_SUM(sin => x(N) xor c(N),

cin => y(N) and x(N) and c(N),

sout => z(N),

cout => c(N+1));

If someone has an idea how to force quartus to _not_ split this into two LE it should be great.