How to customize the execution of commands in Сmake add_custom_command?

Question

CMake

help generation needs to be automated.
Two commands each with three arguments.
It is necessary that the help is compiled in the working directory, and then it is copied to the output,
wrote like this:

add_custom_command(
    OUTPUT ${STATISTIC_DOC_OUTPUT_DIR}
    COMMAND qhelpgenerator
    ARGS
        doc.qhp -o
        doc.qch
    COMMAND qcollectiongenerator
    ARGS
        StatisticHelp.qhcp -o
        StatisticHelp.qhc
    WORKING_DIRECORY ${STATISTIC_DOC_SRC}
)

the problem is that when building, the files are not created where I specified the output.