You are asking for the "vertical sync of the monitor". Vertical sync is a graphics card setting that locks the frame rendering rate to the monitor refresh rate. According to NVida, "This improves image quality by eliminating horizontal tearing effects in the 3D image." Do you want to know whether vertical sync is on or off or were you looking for the refresh rate of the monitor? I don't know how to do the former, but you can get the latter this way:
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 Long
dmPelsWidth As Long
dmPelsHeight As Long
dmDisplayFlags As Long
dmDisplayFrequency As Long
End Type
Private Declare Function EnumDisplaySettings Lib "user32.dll" Alias _
"EnumDisplaySettingsA" (ByVal lpszDeviceName As String, _
ByVal iModeNum As Long, ByRef lpDevMode As DEVMODE) As Long
Private Function GetRefreshRate() As Long
Dim dm As DEVMODE
dm.dmSize = Len(dm)
EnumDisplaySettings vbNullString, ENUM_CURRENT_SETTINGS, dm
GetRefreshRate = dm.dmDisplayFrequency
End Function