Obtaining the time-dependent O-D demand is often a challenging and time consuming task in micro simulations such as Paramics . In this paper, we develop a three-step procedure to expedite this process. The procedure first translates various features of road sections into nodes and links with known capacities to convert a micro simulation network into a network suitable for macroscopic models. A logit path flow estimation module is then used to obtain an initial time-dependent O-D demand pattern. This pattern is in turn used as a starting point by the O-D estimator embedded in a micro simulation model, Paramics in this case, to perform its internal O-D estimation. This procedure is applied to a network in southern California, and the initial results show that it can significantly speed up the O-D estimation process for micro simulation applications.