Function zf(s As String) As Boolean

  zf = False

If  s >= "A" And s <= "Z" Or s >= "a" And s <= "z"  Then

          ①       

  End If

End Function

Private Sub rev_Click()

Dim s As String, ch As String, rv As String, rv1 As String

Dim i As Integer, j As Integer, k As Integer

s = Text1.Text

rv = "" : i = 1

Do While True

  ch = Mid(s, i, 1)

  Do While Not zf(ch) And i < Len(s)

    rv = rv + ch

    i = i + 1

    ch = Mid(s, i, 1)

  Loop

  j = i

  ch = Mid(s, j, 1)

  Do While zf(ch) And j <= Len(s)

           ②        

              If j > Len(s) Then Exit Do

    ch = Mid(s, j, 1)

  Loop

  rv1 = ""

  For                   '改错

    rv1 = Mid(s,k,1)+rv1

  Next k

  rv = rv + rv1

If j <= Len(s) Then rv = rv + Mid(s, j, 1)

  i = j + 1

  If i > Len(s) Then Exit Do

Loop

Text2.Text = rv

End Sub

① ②