运行VB 6，向窗体添加7个Label控件、1个Timer控件、3个Text文本输入框以及4个Command按钮
原理简介：用Timer控件的True或者False值，控制倒计时的开始，当到达设定时间的时候，弹出对话框提示断开连接。
Option Explicit
Dim Hours As Integer
Dim Minutes As Integer
Dim Seconds As Integer
Dim time As Date
Private Declare Function RasHangUp Lib "RasApi32.dll" Alias "RasHangUpA" (ByVal hRasConn As Long) As Long
Private Declare Function RasEnumConnections Lib "RasApi32.dll" Alias "RasEnumConnectionsA" (lprasconn As Any, lpcb As Long, lpcConnections As Long) As Long
Const RAS95_MaxEntryName = 256
Const RAS95_MaxDeviceName = 128
Const RAS_MaxDeviceType = 16
Private Type RASCONN95
dwSize As Long
hRasConn As Long
szEntryName(RAS95_MaxEntryName) As Byte
szDeviceType(RAS_MaxDeviceType) As Byte
szDeviceName(RAS95_MaxDeviceName) As Byte
End Type
下面一段代码是对Timer的控制，以及到设定时间的时候断开连接的代码
Private Sub Timer1_Timer()
Timer1.Enabled = False
If (Format100 100time, "hh") && ":" && Format100 100time, "nn") && ":" && Format100 100time, "ss"))〈〉"00:00:00" Then
time = DateAdd("s", -1, time)
Label1.Visible = False
Label1.Caption = Format100 100time, "hh") && ":" && Format100 100time, "nn") && ":" && Format100 100time, "ss")
Label1.Visible = True
Timer1.Enabled = True
Else
Timer1.Enabled = False
End If
If Label1.Caption = "00:00:01" Then
dsdklj.WindowState = 0
Command1.Enabled = True
MsgBox "时间到了，正在断开连接"
Dim lngRetCode As Long
Dim lpcb As Long
Dim lpcConnections As Long
Dim intArraySize As Integer
Dim intLooper As Integer
ReDim lprasconn95(intArraySize) As RASCONN95
lprasconn95(0).dwSize = 412
lpcb = 256 * lprasconn95(0).dwSize
lngRetCode = RasEnumConnections(lprasconn95(0), lpcb, lpcConnections)
If lngRetCode = 0 Then
If lpcConnections〉0 Then
For intLooper = 0 To lpcConnections-1
RasHangUp lprasconn95(intLooper).hRasConn
Next intLooper
Unload Me
Else
MsgBox "时间到了，没有拨号网络连接"
Unload Me
End If
End If
End If
End Sub
