In two-tier femtocell networks, adjusting the transmission powers of femtocell base stations such that indoor users receive high signal quality while limiting leakage to outdoor users, is an important problem. This paper proposes a novel distributed and self optimized power adjustment algorithm for two-tier femtocell networks, in which a base station adjusts the transmission power based on the signal quality of neighboring base stations. Achieving fairness among users with minimal information exchange is aimed. There are no predefined target parameters used to adjust transmission power, contrary to existing approaches in the literature. The convergence properties of the algorithm under fixed and time varying communication infrastructures are investigated. The performance is further verified by simulations and comparisons to other algorithms for the coverage problem.