Sets the WatermarkFileLandscape member of the BlackIceDEVMODE.
SetWmImageFileforLandscape(pDevMode As Long, WatermarkFile As String) As Boolean
Input value: pDevMode - handle to the BlackIceDEVMODE structure.
Input value: WatermarkFile - Path and name of the watermark.
Return value - TRUE on success, otherwise FALSE.
NOTE: For 32-bit applications, use pDevMode as Integer, instead of Long.