Detailed trace analysis of MPI applications is essential for performance engineering, but growing trace sizes and complex communication behaviour often render comprehensive visual inspection impractical. This work presents a trace-based calculation of time-resolved values of standard MPI performance metrics, load balance, serialisation, and transfer efficiency, by discretising execution traces into fixed or adaptive time segments. The implementation processes Paraver traces postmortem, reconstructing critical execution paths and handling common event anomalies, such as clock inconsistencies and unmatched MPI events, to robustly calculate metrics for each segment. The calculated per-window metric values expose transient performance bottlenecks that the timeaggregated metrics from existing tools may conceal. Evaluations on a synthetic benchmark and real-world applications (LaMEM and ls1-MarDyn) demonstrate how time-resolved metrics reveal localised performance bottlenecks obscured by global aggregates, offering a lightweight and scalable alternative even when trace visualisation is impractical.