设计一个倒计时程序，用户在倒计时文本框中输入倒计时的分钟数，按开始键开始倒计时，按停止键结束。

Dim i As Integer
Dim a As Double
Dim h, m, s As Integer
Dim T As Double
Private Function TimeDisPlay(n As Double) As String '显示时钟函数
Dim h, m, s As Integer
Dim i As Integer
h = Int(n / 3600)
m = Int((n Mod 3600) / 60)
s = n Mod 60
TimeDisPlay = Format(CStr(h), "00") & ":" & Format(CStr(m), "00") & ":" & Format(CStr(s), "00")
End Function
Private Sub Command1_Click()
a = InputBox("清输入定时分钟数")
T = a * 60 '换算为秒
End Sub

Private Sub Command2_Click()
Slider1.Min = 0
Slider1.Max = T
Timer1.Enabled = True
Timer1.Interval = 1000 '设置计时器为1秒运行一次
End Sub

Private Sub Form_Load()
Slider1.Max = 100
Slider1.Min = 0
Timer1.Enabled = False
End Sub

Private Sub Timer1_Timer()
Text1.Text = TimeDisPlay(T)
T = T - 1
i = i + 1
Slider1.Value = i
If T = 0 Then
Timer1.Enabled = False
MsgBox ("倒计时结束！")
End If
End Sub

哦，忘了提醒，是要求用VB程序编写的代码，由于是初学者，我不会，因此来需求帮助，谢谢哦