Можно.
ms-help://MS.MSDNQTR.2003FEB.1033/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/createwindow.htm
lpParam
CreateWindow Function
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Parameters
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[in] Pointer to a value to be passed to the window through the CREATESTRUCT structure passed in the lpParam parameter the WM_CREATE message. If an application calls CreateWindow to create a multiple-document interface (MDI) client window, lpParam must point to a CLIENTCREATESTRUCT structure.