This UDF was created as part of Trac Ticket requests: #2624, #2629 and one users attempt at creating something closely related to what was requested >> >GUIRegisterMsg UDF. See the function below. Thanks. PS As usual this doesn't use a global variable for maintaining the internal array. Like it or hate I don't mind. ; Initial idea by mLipok: http://www.autoitscript.com/forum/topic/162515-guiregistermsg-udf/ ; Compared to mine, mLipok's idea was limited to a certain set of WM_MESSAG