Problem with plotyy in GUI

Hello,

I have a problem with the plotyy function in my GUI (not created with GUIDE). In the beginning of my software I initialize the corresponding axes:

      g.hPlot2D = axes('Parent', hAv, ...
                         'Color', 'None',...
                         'OuterPosition', AXES_FULL);

"hAv" and "AXES_FULL" are variables referring to the Parent and position.

Later I try to update my axis using the following statement in a different function:

    g = guidata(hFig);
    h = g.hPlot2D;
    cla(h);
    plotyy(h, x1, y1, x2, y2);

This procedure worked without any problems for a simple plot but it does not work out for plotyy. Instead it creates the second plot (for the right y-axis) below the first one (instead of on top of it). I think that I might have to initialize the axes for the plotyy differently but I'm not sure how to do that. Could you help me with that?

Thank you very much! Johannes