How to change a text-Field on the MasterPage

I need to change a text-field on the masterpage:

Formular1.#pageSet[0].Seite1.Schaltfläche1::click - (JavaScript, client)

// what is wrong with this code?

xfa.resolveNode("TestForm.#pageSet.Seite1.FP_Formular").rawValue="test"; //does not work

Formular1.Masterseite.Seite1.FP_Formular.rawValue="Test"; //does not work either

What do I do wrong?

Thanks for any help

Bruno