Towards Determining \phi_1 with B\to D^(*)\bar{D}^(*)

We present an isospin analysis of the decay modes B\to D\bar{D}, D^\bar{D}, D\bar{D}^ and D^\bar{D}^, which allows determination of the final-state interaction phases. As these transitions have branching ratios of the order 10^{-4} or larger, they could be useful in detecting the CP- violating phase \phi_1 \equiv \arg (-V^{cb} V{cd} V_{tb} V^_{td} ) in the first-round experiments of a B-meson factory. The problem of penguin pollution may still be present. Once the Kobayashi-Maskawa matrix elements are known, it is possible to obtain the magnitudes and relative phases of hadronic matrix elements for B\to D^{()}\bar{D}^{()}. This will in turn lead to some information about the penguin pollution.