The ItemWindowHostCreateStyle property specifies the window styles of the ActiveX's container window, when a new ActiveX control is inserted using the InsertControlItem method. The ItemWindowHostCreateStyle property has no effect for non ActiveX items. The ItemWindowHostCreateStyle property must be called during the AddItem event, like in the following samples. Generally, the ItemWindowHostCreateStyle property is useful to include WS_HSCROLL and WS_VSCROLL styles for a IWebBrowser control ( WWW browser control ), to include scrollbars in the browsed web page.

Some of ActiveX controls requires additional window styles to be added to the container window. For instance, the Web Brower added by the Gantt1.Items.InsertControlItem(, "https://www.exontrol.com") won't add scroll bars, so you have to do the following:

First thing is to declare the WS_HSCROLL and WS_VSCROLL constants at the top of your module:

Private Const WS_VSCROLL = &H200000
Private Const WS_HSCROLL = &H100000

Then you need to to insert a Web control use the following lines:

Dim hWeb As HITEM
hWeb = Gantt1.Items.InsertControlItem(, "https://www.exontrol.com")
Gantt1.Items.ItemHeight(hWeb) = 196

Next step is adding the AddItem event handler:

Private Sub Gantt1_AddItem(ByVal Item As EXGANTTLibCtl.HITEM)
    If (Gantt1.Items.ItemControlID(Item) = "https://www.exontrol.com") Then
        ' Some of controls like the WEB control, requires some additional window styles ( like WS_HSCROLL and WS_VSCROLL window styles )
        ' for the window that host that WEB control, to allow scrolling the web page
        Gantt1.Items.ItemWindowHostCreateStyle(Item) = Gantt1.Items.ItemWindowHostCreateStyle(Item) + WS_HSCROLL + WS_VSCROLL
    End If
End Sub