TaskPanel: gradient pouring of group header

Hello All,
I created a simple SDI application added TaskPanel.
Now I want to fill both background of TaslPanel and Group header rect with gradient.
In regards to the background of TaskPanel I simply override FillTaskPanel function in my custom paint manager and fill it by gradient using my spec function.
But how can I fill group header the such way.
I tryed to override GetGroupColors() but it was not helpfull for me.
How can I resolve this trouble? How can I fill group header rect with two color where one color will be go to the other by gradient?

I overrided DrawGroupCaption and it was helpful for me. But once I override this method the group icon is not displayed. I can retrive its index:
int CTaskPanelPaintManager::DrawGroupCaption(CDC* pDC, CXTPTaskPanelGroup* pGroup, BOOL bDraw)
{
    //....
    int iconIndex = pGroup->GetIconIndex();
    //HICON groupIcon =
    //pDC->DrawIcon(0, 0, groupIcon);
}
But how can I get the appropriate icon by index.
Thank you

But how can I force updating group header height? I mean DrawGroupCaption function is called for the header height only one time when application is started. In all other cases this function is called for drawing only (parameter bDraw = true). I need to change group header height dinamically but how can I update this header so that new header was applied?