Option Explicit

Dim m As Long

Private Sub Command1_Click()
    Timer1.Enabled = True
    m = Val(Text1.Text) * 60
    Label1.Caption = "现在开始倒计时"
    Command1.Visible = False
End Sub

Private Sub Timer1_Timer()
    m = m - 1
    If m < 0 Then
       Timer1.Enabled = False
       MsgBox "时间到! ", O, "倒计时"
       Label1.Caption = "请输入计时的分钟数"
       Text1.Text = ""
       Command1.Visible = True
    Else
        Text1.Text = m
End Sub
做倒计时器，编译时提示变量未定义是怎么回事，请高手解答