how to set client window hight

You can do like this in OnSize.(Just a pseudo code)

if(m_bSizeAvailable == TRUE)
{
    CRect tempRect;
    m_wndToolBar.GetItemRect(0,&tempRect);
    m_wndToolBar.SetSizes(CSize(tempRect.Width(),cy/10),CSize(16,15));
    m_wndToolBar.SetHeight(cy/10);
}
CFrameWnd::OnSize(nType, cx, cy);

you have to take care of lot of things like,
The button Image size (2nd parameter in SetSizes() function).Because if the images size must be less than the button size.(atleast 7 pixels on x and 6 pixels on y).