In this study, we propose that a molecular junction with a sharp Negative Differential Resistance (NDR) current peak could improve the selectivity, thereby functioning as a potential molecular sensor for molecule recognition. Using DFT-NEGF simulations, we investigate the connection between molecule-molecule coupling, molecule-electrode coupling and the corresponding NDR peak shape. Based on this analysis we propose three design rules to control the sensitivity of a sensor and determine that one mechanism for NDR is for a localised molecular orbital involved in resonant tunneling to enter and leave the bias window. Our findings provide useful insight into the development of single molecule sensors for molecule recognition.