一道VB填空题，谢谢帮忙！

Private Sub Command1_Click()
Dim St As String, Ch As String
Dim Char As String, I As Integer
St = Text1.Text
For I = 1 To len(St)
Ch = Mid(St, I, 1)
Select Case Ch
Case "A" To "Z"
Ch=Lcase(Ch)
Case "a" To "z"
Ch=ucase(Ch)
Case Else
Ch="*"
End Select
Char = Char + Ch
Next I
St = ""
For I = 1 To Len(Char)
St =mid(Char,I,1) & St
Next I
Text2 = St
End Sub

只有填n-1才满足要求