If you realy want to control a MessageBox. Check out this API.

Code:
Private Declare Function MessageBox Lib "user32" Alias "MessageBoxA" _
  (ByVal hwnd As Long, ByVal lpText As String, ByVal lpCaption As String, _
  ByVal wType As Long) As Long

Public Const MB_ABORTRETRYIGNORE = &H2&
Public Const MB_APPLMODAL = &H0&
Public Const MB_DEFAULT_DESKTOP_ONLY = &H20000
Public Const MB_DEFBUTTON1 = &H0&
Public Const MB_DEFBUTTON2 = &H100&
Public Const MB_DEFBUTTON3 = &H200&
Public Const MB_DEFMASK = &HF00&
Public Const MB_ICONASTERISK = &H40&
Public Const MB_ICONEXCLAMATION = &H30&
Public Const MB_ICONHAND = &H10&
Public Const MB_ICONINFORMATION = MB_ICONASTERISK
Public Const MB_ICONMASK = &HF0&
Public Const MB_ICONQUESTION = &H20&
Public Const MB_ICONSTOP = MB_ICONHAND
Public Const MB_MISCMASK = &HC000&
Public Const MB_MODEMASK = &H3000&
Public Const MB_NOFOCUS = &H8000&
Public Const MB_OK = &H0&
Public Const MB_OKCANCEL = &H1&
Public Const MB_RETRYCANCEL = &H5&
Public Const MB_PRECOMPOSED = &H1
Public Const MB_SETFOREGROUND = &H10000
Public Const MB_SYSTEMMODAL = &H1000&
Public Const MB_TASKMODAL = &H2000&
Public Const MB_TYPEMASK = &HF&
Public Const MB_USEGLYPHCHARS = &H4
Public Const MB_YESNO = &H4&
Public Const MB_YESNOCANCEL = &H3&
And use thos one under a Event or something.
Code:
Call MessageBox(0, "Hi There Stranger", App.Title, MB_OK Or _
  MB_ICONINFORMATION Or MB_SYSTEMMODAL)
GoodLuck....