It is easy to set tooltips for standard AutoIt GUI controls by calling GUICtrlSetTip(). But what if you want to reflect some dynamically changing data in that tooltip or you have some custom control what you only know about is a HWND (like a ListView header)? In this case Common Controls API and the notification message TTN_GETDISPINFO is the way to go. Almost everything you need is in the GuiToolTip.au3 (Standard UDF). However _GUIToolTip_AddTool() of all functions there has small functionalit