The radio flux measurement of the compact extragalactic objects are known to show two types of variablity i.e. intrinsic and extrinsic. Some of the unusual minima in the flux measurement seem to involve large structures in the interstellar medium. In this article we outline a simple ray approach for simulation of these minima in the flux measurement. Simulation will help in estimating the physical parameters of these large scale irregularities or structures in the interstellar medium. Some preliminary results of the simulation will also be described.