I need to acquire the client-area mouse coordinates in a window of a third party application. I have used GetCursorPos and ScreenToClient to get the mouse coordinates when the scrollbars are positioned at the top-left position. The client area of the window who’s coordinates I need are usually much larger then the window itself. If you use ScreenToClient in the window when the scrollbars are positioned a few 1000 pixels to the right and down from the upper left corner you will get the position of the mouse pointer relative to the upper left corner of the visible rectangle. Is there a way to get the difference between the upper left corner of the other apps window and the upper left corner of the visible area of the same window?