Hi Petchy,
teste ce petit code:
Declare Function GetActiveWindow32 Lib "USER32" Alias _
"GetActiveWindow" () As Integer
Declare Function SendMessage32 Lib "USER32" Alias _
"SendMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long
Declare Function ExtractIcon32 Lib "SHELL32.DLL" Alias _
"ExtractIconA" (ByVal hInst As Long, _
ByVal lpszExeFileName As String, _
ByVal nIconIndex As Long) As Long
Sub ChangeXLIcon()
Dim h32NewIcon As Long
Dim h32WndXLMAIN As Long
h32NewIcon = ExtractIcon32(0, "Notepad.exe", 0) 'à modifier avec l´image correspondande
h32WndXLMAIN = GetActiveWindow32()
SendMessage32 h32WndXLMAIN, &H80, 1, h32NewIcon 'Icon big
SendMessage32 h32WndXLMAIN, &H80, 0, h32NewIcon 'Icon small
End Sub