包含PictureBox的面板在背景更改时闪烁。我怎么能消除这个？

I have a panel with the BackgroundImage set that I'm using as a button. The panel also contains a PictureBox with a png image loaded so that parts of the image are transparent and the panel image shows through. On MouseDown I change the panels BackgroundImage, then on MouseUp I change it back again. The problem is that when the panel image changes, the PictureBox flickers badly when redrawing its transparent areas. I have a panel with the BackgroundImage set tha