At the Norwegian Defence Research Establishment (FFI) we investigate how to increase combat effectiveness in land force operations. As part of this work we need to conduct detailed, entity-level simulations of battalion to brigade level operations, to assess the performance of different land force structures and operational concepts. Traditional constructive simulation systems often do not have the required level of resolution, are too complex and cumbersome to use, or are not flexible enough with respect to representation of new technologies (e.g. new sensor systems, weapon systems, and protection systems). Previously, we have successfully employed Virtual Battlespace (VBS) for several smaller-sized (platoon to company) virtual simulation experiments for evaluating the operational benefit of new technologies and new concepts. Recent improvements allow simulation of more than a thousand constructive, semi-automated entities in VBS, but it currently lacks an appropriate user interface for controlling constructive entities. We are developing an easy-to-use, web-based graphical user interface (GUI) system for controlling constructive entities simulated in VBS. So far we have developed functionality for controlling indirect fire entities and maneuver entities. In the future we plan to extend the system with functionality for controlling combat service and support entities simulated in VBS, and air and air defense entities possibly simulated in VR-Forces. Since we conduct simulations for experimentation and analysis purposes, and not command and staff training, the system has been designed to only require a minimum amount of input from the operators. It is a goal that military officers should be able to control the entities with minimal instruction. In addition, the simulations should be conducted with a minimum number of operators on each side. In this paper we describe the overall design and implementation of the GUI system, as well as the experiences from the initial experiments with the system.