Private Declare Function ChangeDisplaySettings Lib "user32.dll" Alias _
"ChangeDisplaySettingsA" (lpDevMode As DEVMODE, ByVal dwFalgs As Long) As Long

Private Const DM_BITSPERPEL = &H40000
Private Const DM_PELSWIDTH = &H80000
Private Const DM_PELSHEIGHT = &H100000
Private Const CCHDEVICENAME = 32
Private Const CCHFORMNAME = 32

Private Type DEVMODE
dmDeviceName As String * CCHDEVICENAME
dmSpecVersion As Integer
dmDriverVersion As Integer
dmSize As Integer
dmDriverExtra As Integer
dmFields As Long
dmOrientation As Integer
dmPaperSize As Integer
dmPaperLength As Integer
dmPaperWidth As Integer
dmScale As Integer
dmCopies As Integer
dmDefaultSource As Integer
dmPrintQuality As Integer
dmColor As Integer
dmDuplex As Integer
dmYResolution As Integer
dmTTOption As Integer
dmCollate As Integer
dmFormName As String * CCHFORMNAME
dmUnusedPadding As Integer
dmBitsPerPel As Integer
dmPelsWidth As Long
dmPelsHeight As Long
dmDisplayFlags As Long
dmDisplayFrequency As Long
End Type

Private Sub Command1_Click()
Dim dm As DEVMODE
' Устанавливаем разрешение 640x480
dm.dmPelsWidth = 640
dm.dmPelsHeight = 480
' Устанавливаем цветовую палитру 256 цветов
dm.dmBitsPerPel = 8
dm.dmSize = Len(dm)
dm.dmFields = DM_PELSWIDTH + DM_PELSHEIGHT + DM_BITSPERPEL
ChangeDisplaySettings dm, 0
End Sub