ShowInTaskBar property

How can I turn off the ShowInTaskBar property for MDI form?
I notice the MDI form doesn't have this property, how would I accomplish this through vb code? Thanks!

In the MDI Form:

Code:

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Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Const GWL_EXSTYLE = (-20)
Private Const WS_THICKFRAME = &H40000

Private Sub MDIForm_Load()
    Call SetWindowLong(hwnd, GWL_EXSTYLE, _
    GetWindowLong(hwnd, GWL_EXSTYLE) Xor WS_THICKFRAME)
End Sub

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