Mobility and channel modeling is a very crucial task for the simulation of Vehicular Ad Hoc Network (VANET) scenarios. In this paper we present a new mobility modeling approach for OMNeT++ and the INET-Framework. The approach allows generation and deletion of nodes during simulation time and reduces the number of events significantly. To demonstrate and test the functionality of the new modeling concept we designed a simple, yet effective mobility model called Manhattan Grid Mobility Model (MGMM), which can be coupled with a new channel modeling approach, incorporating obstacles such as buildings for the reception power calculation. In our paper we describe both, the general concept of our idea, the realization using the MGMM and the Dual-Slope channel model, and give an overview on related work.