MrVietA2, To hide the taskbar button for the MsgBox, just set the hwnd parameter: #include <GUIConstantsEx.au3>
$hGUI = GUICreate("Test", 500, 500)
$hButton = GUICtrlCreateButton("Test", 10, 10, 80, 30)
GUISetState()
While 1
Switch GUIGetMsg()
Case $GUI_EVENT_CLOSE
Exit
Case $hButton
MsgBox(0,"Hello","How are you ?", 0, $hGUI)
EndSwitch
WEndM23