In this paper we present the design of a Variable Structure Interacting Multiple Model (VS-IMM) estimator for tracking evasive ground targets using Moving Target Indicator reports obtained from an airborne sensor. In order to avoid detection by the MTI sensor, the targets use a move- stop-move strategy, where a target deliberately stops or moves at a very low speed for some time before accelerating again. In this case, when the target's radial velocity (along the line of sight from the sensor) falls below a certain Minimum Detectable Velocity, the target is not detected by the sensor. Under these conditions, the use of an estimator, which does not take care of this move-stop-move motion explicitly, can result in broken tracks. The tracker proposed in this paper handles the evasive move-stop-move motion via the VS-IMM estimator, where the tracker mode set is augmented with a stopped-target model when the estimated speed of the target falls below a certain threshold. Using this additional stopped-target model, the target state is kept alive even in the absence of a measurement. A simulated scenario is used to illustrate the selection of design parameters and the operation of the tracker. Performance measures are presented to contrast the benefits of the VS-IMM estimator, which uses the stopped-target model, over a standard IMM estimator.