The Clip property of the Cursor is the rectangle within which the mouse cursor is confined, or its value is Nothing if the mouse can move over the entire screen. This rectangle is in screen coordinates, so you must do some conversions if you want to confine the mouse to an object on the form:
' Clip the mouse to the TextBox1 control's client area.Cursor.Clip = TextBox1.RectangleToScreen(TextBox1.ClientRectangle)' ...(do something here) ...' Free the mouse cursor.Cursor.Clip = Nothing