I noticed that multi threaded msgbox works fine but multi threaded _GUICtrlEdit_AppendText doesnt work so fine anymore. Usage: 1) save UDF as ThreadCreate.au3 2) Before you say that multithreading is impossible, run code below "Here's working Example" 3) If you want help me finding out what's wrong in my not working example, you can run this. Remarks: I've also noticed that when you put while loop in your threaded function, autoit crashes with out reason but when you just hav