[CMake] add_custom_command problem

[Andrea Galeazzi]

I'm trying to invoke a program which increment the build number on a 
header file. I'm currently using the following statement:
add_custom_command(OUTPUT "./BuildNumber.h" COMMAND "java" ARGS "-jar"
                                         "${TOOLS}\\BuildNumberUpdater.jar"
                                         
"${PROJECT_PATH}\\Frameworks\\Win32\\BuildNumber.h"
                                         DEPENDS ${SOURCES}
                                         COMMENT "Changing the build 
numeber")
But the command is never invoked. Surely there's something wrong or 
something that I don't understand, but what?