Modify the value of a RegisteredPanel in Nuke PyQt

Question

I created a registered panel in Nuke and I am trying to modify its content by pressing a button in a different Qt Window.

The panel is using the following code :

import nuke

try:
  ## < Nuke11
    import PySide.QtGui as QtGui
    import PySide.QtCore as QtCore

except:
  ## >= Nuke11
    import PySide2.QtCore as QtCore
    import PySide2.QtGui as QtGui
    import PySide2.QtWidgets as QtGui
    from PySide2.QtWidgets import QWidget as QWidget


class Example(QtGui.QWidget):
    def __init__(self):
        super(Example,self).__init__()
        self.comboBox = QtGui.QComboBox()
        self.comboBox.addItems(['Item 1','Item 2','Item 3','Item 4'])


        layout = QtGui.QVBoxLayout(self)
        layout.addWidget(self.comboBox)

pane = nuke.getPaneFor("Example.panel")
panels.registerWidgetAsPanel('Example', 'Example',"", True).addToPane(pane)

Now I am opening another window of a different tool. I am trying to create a bridge between the two tools. I want to modify the value of the ComboBox in the panel by pressing a button in my new Window.

Here is the code for the window :

import nuke
try:
  ## < Nuke11
    import PySide.QtGui as QtGui
    import PySide.QtCore as QtCore

except:
  ## >= Nuke11
    import PySide2.QtCore as QtCore
    import PySide2.QtGui as QtGui
    import PySide2.QtWidgets as QtGui
    from PySide2.QtWidgets import QWidget as QWidget


def Panel():
    class myPanel(QtGui.QWidget):
        def __init__(self):
            super(myPanel, self).__init__()
            self.setWindowFlags(QtCore.Qt.WindowStaysOnTopHint)
            self.setFixedWidth(520)
            self.setFixedHeight(100)
            layout = QtGui.QVBoxLayout(self)

            Button = QtGui.QPushButton('Use Item 4')
            Button.clicked.connect(self.modifyPanel)

            layout.addWidget(Button)

        def modifyPanel(self):
            print ''
            #This is where I am stuck, how to access and modify the Panel

    myPanel = myPanel()
    myPanel.show()
Panel()

Thanks a lot, Roman