REM source code is from :
REM http://abstractvb.com/code.asp?A=822

Attribute VB_Name = "Module1"
Public Const SPI_SETDESKWALLPAPER = 20
Public Const SPIF_SENDWININICHANGE = &H2
Public Const SPIF_UPDATEINIFILE = &H1

Public Declare Function SystemParametersInfo _
    Lib "user32" Alias "SystemParametersInfoA" _
    (ByVal uAction As Long, _
    ByVal uParam As Long, _
    ByRef lpvParam As Any, _
    ByVal fuWinIni As Long) As Long

Public Sub SetWallPaper(strFileName As String)
    Dim lngResult As Long
    Dim lngFlags As Long
            
    lngFlags = SPIF_UPDATEINIFILE Or SPIF_SENDWININICHANGE
    lngResult = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, ByVal strFileName, lngFlags)
End Sub



Sub Main()

    If Hour(Time) >= 4 And Hour(Time) <= 10 Then
        SetWallPaper "c:\vaio\dawn.bmp"
    ElseIf Hour(Time) >= 11 And Hour(Time) <= 16 Then
        SetWallPaper "c:\vaio\daytime.bmp"
    ElseIf Hour(Time) >= 17 And Hour(Time) <= 19 Then
        SetWallPaper "c:\vaio\sunset.bmp"
    Else
        SetWallPaper "c:\vaio\midnight.bmp"
    End If

End Sub