  We note that in decays of the type $B^0 \to P^0P^0X^0$, where $P^0$ and $X^0$
represent any CP eigenstate spin-0 neutral particles, the final state is a CP
eigenstate. We consider the possibilities for studying time-dependent CP
violation in decays of this type at $B$ factories with high luminosity, with
particular attention to $B^0 \to \ks \ks \ks$. We also comment on some cases
where $X^0$ has non-zero spin, and decays of the type $B^0 \to P^0 Q^0 X^0$,
where the three final state particles are different spin-0 CP eigenstates.
