大家帮忙用VB做一个倒计时器。

Dim i As Integer
Private Sub Command1_Click()
i = 20
Timer1Enabled = True
Command1Enabled = False
End Sub
Private Sub Form_Load()
Timer1Enabled = False
Timer1Interval = 1000
End Sub
Private Sub Timer1_Timer()
i = i - 1
MeCaption = i
If i = 0 Then Timer1Enabled = False: Command1Enabled = True: MsgBox "结束"
End Sub

Start按钮，点击开始倒记时
Text1控件，显示剩余时间
时钟控件Timer1, interval=500, enable=false
代码如下：
Dim TimeOut as long
Private sub Start_Click()
TimeOut=Timer + (30 60) '定时30分钟,1800秒后停止
Timer1enable=true '开始倒计时
End sub
private sub Timer1_timer()
dim R as long
dim S as long
dim M as long
dim H as long
R=timeout-timer '计算剩余时间
M=R mod (6060) '余数为不足1小时部分
H=（R-M）/ (6060) '得到小时部分
S=M mod 60 '余数为不足1分钟部分,得到秒数部分
M=(M-S)/60 '得到分钟部分
timer1text=format(h,"00") & ":" & format(m,"00") & ":" & format(s,"00") '显示剩余时间
if h=0 and m=0 and s=0 then
timer1enable=false
Shell ("c:\windows\system32\shutdownexe /s /t 1") '时间到，关机
end if
end sub
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