I don't think it's possible with only OpenCV, you have to use OS API or eventually you may use QT(http://www.codeprogress.com/cpp/libraries/qt/QtHideMouseCursor.php#.UjGpZD-rGoE) - it's quite easy to use it with OpenCV.
looks exactly what I want cyriel! however, I dont see the way of integrating this with my current opencv windows. How do I connect Qt with my current functions such as: namedWindow(name, CV_WINDOW_AUTOSIZE ); cvShowImage(name, image);
Qt is integrated with OpenCV, at least a bit - look at this opencv.willowgarage.com/documentation/cpp/ Note that first you have to compile OpenCV with Qt. Google search for "opencv qt" or "opencv qt widget" gives more informations about integrating Qt and OpenCV.