A system includes a string disposed in a wellbore, a first valve coupled to the string, the first valve including a sleeve having an engagement profile with a first coded sequence, a second valve coupled to the string, the second valve including a sleeve having an engagement profile with a second coded sequence that differs from the first coded sequence of the first valve, and a first dart flow transportable through the string, the first dart including a collet finger having a first coded sequence configured to restrict the collet finger from matingly engaging the engagement profile of the first valve while permitting the collet finger to engage the engagement profile of the second valve, wherein the first dart actuates the sleeve of the second valve between first and second positions in response to the collet finger of the first dart matingly engaging the engagement profile of the second valve.