求这段VB程序每句话的意思

Private Sub Dir1_Chang()File1.Path = Dir1.PathText1.Text = Dir1.PathEnd SubPrivate Sub Drive1_Change()Dir1.Path = Drive1.DriveText1.Text = Drive1.DriveEnd SubPrivate Sub File1_Click()Dim x, yf$ = Dir1.Path + "尀" + File1.FileNameIf Mid(f$,4,1)="1" Then f$=Left(f$,3)+Right(f$,Len(f$) - 4)End If Text1.Text = f$ End Sub Private Sub File1_Dblclick() Dim var As StringMMControl1.Command = "close" On Error GoTo error Picture1.AutoRedraw = Ture var = Right(f$, 3) If var = "wav" Or var = "wav" Then MMControl1.DeviceType = "waveaudio" MMControl1.FileName = f$ Label1.FontSize = 72 Label1.Caption = "WAV" Else If var = "mid" Or var = "MID" Then MMControl1.DeviceType = "" MMControl1.FileName = f$ Label1.FontSize = 72 Label1.Caption = "MIDI" Else If var = "avi" Or var = "VAI" Then MMControl1.DeviceType = "avivideo" MMControl1.File1Name = f$ MMControl1.hWndDisplay = Picture1.hWnd Label1.FontSize = 72 Label1.Caption = "AVI" Else If var = "mp3" Or var = "MP3" Then MMControl1.DeviceType = "" MMControl1.FileName = f$ Label1.FontSize = 72 Label1.Caption = "MP3" Else MMControl1.FileName = f$ MMControl1.DeviceType = "" MMControl1.hWndDisplay = Picture.hWnd Label1.FontSize = 72 Label1.Caption = "VIDEO" End If End If End If End If MMControl1.Command = "open" Exit Suberror:End Sub