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

Private Const WM_MOUSEWHEEL = &H20A ' window message for mouse wheel
Private MouseWheelUp As Boolean     ' true if mouse wheel up, false if down
Public Const GWL_WNDPROC = (- 4 )
Public OldProc1 As Long             ' Holds the old TWndProc for form 1
Public bMouseInGrid As Boolean

Public Function TWndProc1(ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
   'If mainForm.MSHFlexGrd.hWnd = hWnd Then
    If wMsg = WM_MOUSEWHEEL And mainForm.MSHFlexGrd.Visible And _
        bGrdFocus And bMouseInGrid Then ' Have we got a mouse wheel message
        If wParam > 0 Then MouseWheelUp = True Else MouseWheelUp = False
            Select Case MouseWheelUp
                Case True ' mouse up value is found
                    mainForm.MSHFlexGrd.TopRow = IIf(mainForm.MSHFlexGrd.TopRow =  1 , _
                                                    mainForm.MSHFlexGrd.TopRow, _
                                                    mainForm.MSHFlexGrd.TopRow -  1 )
                Case False ' mouse value down is found
                    mainForm.MSHFlexGrd.TopRow = IIf(mainForm.MSHFlexGrd.TopRow >= _
                                                    mainForm.MSHFlexGrd.Rows - 1, _
                                                    mainForm.MSHFlexGrd.Rows - 1, _
                                                    mainForm.MSHFlexGrd.TopRow + 1)
            End Select
    End If
  'End If
  TWndProc1 = CallWindowProc(OldProc1, hWnd, wMsg, wParam, lParam)
End Function