Crie um módulo e copie o conteudo abaixo nele!
Option Explicit
Private Declare Function EnumDisplaySettings Lib "user32" Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As Long, ByVal iModeNum As Long, lpDevMode As Any) As Boolean
Private Declare Function ChangeDisplaySettings Lib "user32" Alias "ChangeDisplaySettingsA" (lpDevMode As Any, ByVal dwFlags As Long) As Long
Const CCDEVICENAME = 32
Const CCFORMNAME = 32
Const DM_PELSWIDTH = &H80000
Const DM_PELSHEIGHT = &H100000
Private Type DEVMODE
dmDeviceName As String * CCDEVICENAME
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 * CCFORMNAME
dmUnusedPadding As Integer
dmBitsPerPel As Integer
dmPelsWidth As Long
dmPelsHeight As Long
dmDisplayFlags As Long
dmDisplayFrequency As Long
End Type
Dim DevM As DEVMODE
Sub ChangeRes(iWidth As Single, iHeight As Single)
Dim a As Boolean, i&
i = 0
Do
a = EnumDisplaySettings(0&, i&, DevM)
i = i + 1
Loop Until (a = False)
Dim b&
DevM.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT
DevM.dmPelsWidth = iWidth
DevM.dmPelsHeight = iHeight
b = ChangeDisplaySettings(DevM, 0)
End Sub
'Muda a resolução da tela (No evento open do form)
'Para chamar
'Call ChangeRes(800, 600)
'Call ChangeRes(640, 480)
'Call ChangeRes(1024, 768)
'Call ChangeRes(1024, 600) e por ai vai...