The development of performance models from real-time system source code can be a time consuming process. It can be difficult to capture actual system timing values to be used in these models. The tool PARTES is introduced. PARTES facilitates the extraction of CSPL (C-based Stochastic Petri net Language) models from an ANSI-C program which has been annotated by the user. These models are then subjected to sensitivity analysis via the SPNP (Stochastic Petri Net Package). The results from analysis can be used to directly identify any potentially problematic timing areas in the original source code.