In order to adapt to the inconstancy of business environments and service requirements, a model of dynamic workflow is defined. It can be used to analyze and implement dynamic processes and process changes automatically. The dynamics of processes depends on many factors including the current state, input data, and customer-defined functions and so on. The effectiveness of process changes can be evaluated through checking both functional and non-functional factors, including soundness, I/O equivalence, compatibility, QoS, and cost of change deployment. The effectiveness of process changes is a paramount indicator to decide the rationality of process changes. Process dynamics May depend on both structural changes and functional changes which constitutes the two methods of process change deployment. Before changes are made, the effectiveness is considered to make a final decision. This paper adopts a DPLWN (Dynamic Programmable Logic Workflow) model based on Petri nets to design and implement dynamic business processes and analyze process changes by presenting an algorithm to evaluate the effectiveness. A prototype is given to deploy online and offline process changes.