You can get that information from the Device Utilization Summary after ISE has finished place and route. You can get a complete breakdown of utilization on a module by module basis if you enable the detailed map report (-detail swtich). If this is a submodule of a larger design then you can get an estimate from the output of XST or whatever synthesis tool front end you are using. Just realize the synthesis report is only an estimate and the build process will likely use more LUTs than are reported in the synthesis due to route throughs and control set restrictions.