...so i tried your code suggestion, but now i get this error:

c:/programme/Qt/4.3.4/include/QtCore/../../src/corelib/kernel/qobject.h static_cast from type `const QObject*' to type `SchulungsplanModel*' casts away constness 200308 line 442 1207906858745 1045

...because (index.model()) returns a const pointer, how do I have to cast correctly??