Bon j'ai bien un début mais...
*******
Module1
*******
Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByRef lParam As Any) As Long
Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Public Const WM_COPYDATA = &H4A
Public Const IPC_PLAYFILE = 100
Type COPYDATASTRUCT
dwData As Long
cbData As Long
lpData As String
End Type
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Form1
*****
Private Sub Command1_Click()
Dim hwndWinamp As Long
Dim data As COPYDATASTRUCT
Dim s As String
s = "c:\file.mp3"
data.dwData = IPC_PLAYFILE
data.lpData = s
data.cbData = Len(s) + 1
hwndWinamp = FindWindow("Winamp v1.x", vbNullString)
SendMessage hwndWinamp, WM_COPYDATA, Me.hwnd, data
End Sub
Winamp est bien ouvert, j'ai bien un fichier file.mp3 dans c:\ mais rien ne se passe?!?

Pourquoi???
Merci à la personne qui pourra me venir en aide!!! ;)