Complex fluid media where molecules are susceptible to forces due, for example, to external magnetic fields, complicates the design of molecular communication systems. In particular, the equations governing the motion of each molecule in time do not typically admit tractable solutions, which makes receiver design challenging for standard signaling schemes; e.g., concentration shift keying. In this paper, we propose a new signaling scheme, which leads to simple expressions for receiver statistics, even when spatially inhomogeneous diffusion and external forces are present. Our scheme exploits the equilibrium statistics of the system, which arise in a wide range of scenarios. We illustrate our approach in a bounded system with inhomogeneous diffusion and external forces determined by a quadratic potential.