I don't think this will work in all cases, can you post the equation in question?
To find the conjugate of a complex number, we know that if it is of the form a+ib, then the conjugate is a-ib. Now say I have a very huge expression containing complex numbers in numerators and denominators which is very tough to reduce in the form a+ib. I have to find its conjugate. Then if I replace every i by -i in the expression, will this resultant expression be the required conjugate?