Option Explicit

Private Sub Form_Load()
    ResizeDisplay True, 1024, 768
End Sub

Private Sub Form_Unload(Cancel As Integer)
    ResizeDisplay (False)
End Sub

Option Explicit

Const WM_DISPLAYCHANGE = &H7E
Const HWND_BROADCAST = &HFFFF&
Const EWX_LOGOFF = 0
Const EWX_SHUTDOWN = 1
Const EWX_REBOOT = 2
Const EWX_FORCE = 4
Const CCDEVICENAME = 32
Const CCFORMNAME = 32
Const DM_BITSPERPEL = &H40000
Const DM_PELSWIDTH = &H80000
Const DM_PELSHEIGHT = &H100000
Const CDS_UPDATEREGISTRY = &H1
Const CDS_TEST = &H4
Const DISP_CHANGE_SUCCESSFUL = 0
Const DISP_CHANGE_RESTART = 1
Const BITSPIXEL = 12

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

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
Private Declare Function ExitWindowsEx Lib "user32" (ByVal uFlags As Long, ByVal dwReserved As Long) As Long
Private Declare Function GetDeviceCaps Lib "gdi32" (ByVal hdc As Long, ByVal nIndex As Long) As Long
Private Declare Function CreateDC Lib "gdi32" Alias "CreateDCA" (ByVal lpDriverName As String, ByVal lpDeviceName As String, ByVal lpOutput As String, ByVal lpInitData As Any) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

Public OldX As Long
Public OldY As Long
Public nDC As Long

Private Sub ChangeResolution(x As Long, y As Long, Bits As Long)
    Dim DevM As DEVMODE, ScInfo As Long, erg As Long, an As VbMsgBoxResult
    erg = EnumDisplaySettings(0&, 0&, DevM)
    DevM.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT Or DM_BITSPERPEL
    DevM.dmPelsWidth = x
    DevM.dmPelsHeight = y
    DevM.dmBitsPerPel = Bits
    erg = ChangeDisplaySettings(DevM, CDS_TEST)
    Select Case erg&
        Case DISP_CHANGE_RESTART
            an = MsgBox("You need to restart your computer for new settings to take effect.", vbYesNo + vbSystemModal, "Info")
            If an = vbYes Then
                erg& = ExitWindowsEx(EWX_REBOOT, 0&)
            End If
        Case DISP_CHANGE_SUCCESSFUL
            erg = ChangeDisplaySettings(DevM, CDS_UPDATEREGISTRY)
            ScInfo = y * 2 ^ 16 + x
            SendMessage HWND_BROADCAST, WM_DISPLAYCHANGE, ByVal Bits, ByVal ScInfo
            'MsgBox "Resolution has been changed...", vbOKOnly + vbExclamation, "Resolution Change"
        Case Else
            MsgBox "Display setting is not supported", vbOKOnly + vbCritical, "Error"
    End Select
End Sub

Public Sub ResizeDisplay(ByVal ENABLED As Boolean, Optional ByVal x As Long, Optional ByVal y As Long)
    If ENABLED And Not IsMissing(x) And Not IsMissing(y) Then
        If x And y > 0 Then
            OldX = Screen.Width / Screen.TwipsPerPixelX
            OldY = Screen.Height / Screen.TwipsPerPixelY
            nDC = CreateDC("DISPLAY", vbNullString, vbNullString, ByVal 0&)
            ChangeResolution x, y, GetDeviceCaps(nDC, BITSPIXEL)
        End If
    Else
        If OldX And OldY > 0 Then
            ChangeResolution OldX, OldY, GetDeviceCaps(nDC, BITSPIXEL)
            DeleteDC nDC
        End If
    End If
End Sub