Call with changeResolution(w,h)
--------------------------

'The API's:
Private Declare Function EnumDisplaySettings Lib "user32.dll" Alias "EnumDisplaySettingsA" _
(ByVal lpszDeviceName As Long, ByVal iModeNum As Long, lpDevMode As Any) As Boolean
Private Declare Function ChangeDisplaySettings Lib "user32.dll" Alias "ChangeDisplaySettingsA" _
(lpDevMode As Any, ByVal dwFlags As Long) As Long
Private Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" _
(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

'Types:
Private Type DEVMODE
    dmDeviceName       As String * 32
    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 * 32
    dmUnusedPadding    As Integer
    dmBitsPerPel       As Integer
    dmPelsWidth        As Long
    dmPelsHeight       As Long
    dmDisplayFlags     As Long
    dmDisplayFrequency As Long
End Type

'Now the function itself:
Public Function changeResolution (ByVal width As Integer, ByVal height As Integer)
   Dim dev As DEVMODE
   EnumDisplaySettings 0, 0, dev
   dev.dmFields = &H80000 Or &H100000
   dev.dmPelsWidth = width
   dev.dmPelsHeight = height