The investigation of the dynamics of the interaction of high-energy X-rays and molecules of biological interest requires the energy of the X-rays to be well defined, so that one can establish the dependence of the molecular ionization and fragmentation patterns as functions of the incident beam energy. For this purpose, a versatile system for the monochromatization of the broadband beams produced by an ISOVOLT 160M2 X-ray tube has been designed, constructed and characterized. The monochromator consists of a pair of crystals mounted on two translator tables fixed on a high-precision goniometer, all manufactured by Newport Corp. This configuration allows independent translational motions for the two crystals, associated to a rotational motion of the whole system in respect to the direction of the incident X-ray beam. These motions, together with a convenient choice of the pair of crystals for a given energy range - which depends on the material and orientation of the crystals -, will allow us to cover a wide range of X-rays energies, roughly from few to around 100 keV. However, it has not yet been possible to distinguish energy-defined X-ray peaks with the complete two-crystal system. Some of the possible causes may be related to the large angular dispersion of the incident beam and to the need of more accurate adjustments of the parallelism between both crystals. When this system is fully operational, it will be possible to perform a large variety of experiments in the fields of collision and radiation physics, such as, molecular fragmentation by Xrays, selective fluorescence and diffraction in crystals, real-time evaluation of Xray- induced damage in biological tissues, non-destructive testing of materials, among many other aplications.