Erasing bkground while drawing text

I m working on application which requires automatic scrolling text in a cycle.I m using doc/view for this.I am using WM_TIMER message n drawing the text..but while drawing text on WM_TIMER message its not erasing the previous drawn text..
Thanks in advance.

Try drawing spaces to erase the previous stuff and then draw whatever you wnat. A kind of clumsy way but at least a way.