There is no an new tool.
In SolidWorks Premium and Simulation packages you have SolidWorksSimulation that alows you to do FEA for assemblies.
To use eXpress for assemblies you need to covert them in to single body part.
currently I'm using SolidWorks Premium 2010 sp 4.0 with simulation professional. i tried to run simulationxpress in assembly.SW not allowed run in assembly.
Hi Mohammed: It is not new. It comes with SolidWorks Premium.