Safety-critical distributed control systems must support periodic and aperiodic functions on common hardware (e.g. sending messages on a common data bus). Scheduling techniques that produce a timeline with predefined blocks for periodic functions are used to guarantee deadlines for critical closed loop periodic control functions (i.e. sensor read, control, actuator write). Aperiodic processing occurs in periodic timeline gaps. We develop a technique for binning aperiodic latency sample data using a novel data representation called latency band graphs. A fluid flow analysis produces a small, fixed size set of automatically generated bins dependent only on the timeline defined by periodic traffic. The compact number of bins yeilds a parameterized latency representation suitable for real-time estimation and goodness-of-fit tests. Simulation results show good latency estimates under a broad range of conditions.