Workflow technologies have become an efficient mean for the development of different applications. One wellknown challenge for executing workflows on cloud computing is the resources provisioning. The latter consists in making an appropriate decision when mapping tasks to resources considering multiple objectives that are often contradictory. The problem of resources provisioning for workflow applications in the cloud has been widely studied in the literature. However, the existing works didn't consider the change in workflow instances at runtime. This functionality has become a major requirement to deal with unusual situations and evolutions. In this paper, we present a first step towards the resources provisioning for a dynamic workflow in the cloud. In fact, we propose a provisioning algorithm which takes into account some constraints. After that, we extend it in order to support the dynamic changes of workflow. Our algorithm is evaluated using CloudSim simulator. The different experiments that we present show the efficiency of our approach in terms of financial execution cost and overhead.