[Paraview] Paraview QT plugin

[Tom]

Hi all, I am trying to write my own qt gui which I would like to integrate in 
Paraview. Searching in internet, I did not find anything useful.
But after looking at some examples, I created a header and cxx file with the 
toolbar example illustrated in some tutorials. I created an CMakeList file 
too, by writing as stated in the tutorial:

 FIND_PACKAGE(Qt4 REQUIRED)
 FIND_PACKAGE(ParaView REQUIRED)
 INCLUDE(${PARAVIEW_USE_FILE})

 include(${QT_USE_FILE}) 
 QT4_WRAP_CPP(MOC_SRCS SourceToolbar.h)

 ADD_PARAVIEW_ACTION_GROUP(IFACES IFACE_SRCS 
                         CLASS_NAME SourceToolbar
                         GROUP_NAME "SourceToolbar")
 

 ADD_PARAVIEW_PLUGIN(SourceToolbar "1.0"
                   GUI_INTERFACES ${IFACES}
                   SOURCES ${MOC_SRCS} ${IFACE_SRCS} 
                   SourceToolbar.cxx)

Then I opened the CMake and was trying to run configurate, but it is not 
running. The errors are:

add_executable cannot create imported target "vtkEncodeString" because
another target with the same name already exists.

So, already running a simple example does not work. Can anybody please help?