In the games and anime, no, that is not one of the functions of the PokeDex. Its sole purpose is to give data and info on each Pokemon. However, in the well known Pokemon manga "Pokemon Adventures", the PokeDex is able to stop evolution. The manga isn't official though, it's just an adaptation of the games.
>The Pokédex's function takes over much of the control the games give to the player, being able to prevent a Pokémon's evolution, whereas Trainers without a Pokédex have no choice in the matter. - Bulbapedia