risolto cosi :


codice:
Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Public Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Public Const GWL_WNDPROC = (-4)
Public lpPrevWndProc As Long
Const WM_MOUSEWHEEL = &H20A
Const WHEEL_DELTA = 120
Dim Count As Integer
Function WndProc(ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    If Msg = WM_MOUSEWHEEL Then
        Dim Delta As Long
        Static Travel As Long
        Delta = HiWord(wParam)
        Travel = Travel + Delta
        MouseWheel Travel \ WHEEL_DELTA, LoWord(lParam), HiWord(lParam)
        Travel = Travel Mod WHEEL_DELTA
    End If
    WndProc = CallWindowProc(lpPrevWndProc, hWnd, Msg, wParam, lParam)
End Function

Sub MouseWheel(Travel As Integer, X As Long, Y As Long)
    magazzino.datagrid1.Scroll 0, -Travel
End Sub

Function HiWord(DWord As Long) As Integer
    CopyMemory HiWord, ByVal VarPtr(DWord) + 2, 2
End Function

Function LoWord(DWord As Long) As Integer
    CopyMemory LoWord, DWord, 2
End Function
nell' evento load del form invece:
codice:
 lpPrevWndProc = SetWindowLong(datagrid1.hWnd, GWL_WNDPROC, AddressOf WndProc)
e tutto funge ...............................................