En un modulo colocas:
 
Public Declare Function EnumDisplaySettings Lib "user32.dll" Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As Long, ByVal iModeNum As Long, lpDevMode As Any) As Boolean
Public Declare Function ChangeDisplaySettings Lib "user32.dll" Alias "ChangeDisplaySettingsA" (lpDevMode As Any, ByVal dwFlags As Long) As Long
Public Declare Function GetSystemMetrics Lib "user32" (ByVal nIndex As Long) As Long 
Public Const CCDEVICENAME = 32
Public Const CCFORMNAME = 32
Public Const DM_PELSWIDTH = &H80000
Public Const DM_PELSHEIGHT = &H100000 
Public 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 
Public DevChg As DEVMODE 
Public Sub ChangeRes(iWidth As Single, iHeight As Single)
 Dim a As Boolean
 Dim I&
 I = 0
   Do
    a = EnumDisplaySettings(0&, I&, DevChg)
    I = I + 1
   Loop Until (a = False)
    Dim b&
     DevChg.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT
     DevChg.dmPelsWidth = iWidth
     DevChg.dmPelsHeight = iHeight
     b = ChangeDisplaySettings(DevChg, 0)
End Sub 
Y en el formulario: 
Public Sub CheckRes()
 Dim X As Long, Y As Long
 Dim MsgTitle As String
 Dim MsgStyle As Long
 Dim msg As String
 Dim MsgResponse As Long
  Y = GetSystemMetrics(0)
  X = GetSystemMetrics(1)
  If "" & Y & "x" & X <> "1024x768" Then 'Aqui es donde comparas la resolucion
      MsgBox "La resolución de su monitor es " & Y & "x" & X & " 
      Call ChangeRes(1024, 768) 'Aqui asignas la resolucion que quieres
  End If
End Sub 
Pruebalo...