对一段字符（仅包含大小写字母和数字）加密，加密规则为： ①字母和数字都往后循环顺移3位，如“a”变为“d”，“y”变为“b”；“0”变为“3”，“7”变为“0”②加密后字母在前，数字在后③字母按逆序排列，数字按顺序排列，如输入明文“ab7Z8x3”，这密文为“aCed4016”。

小王利用VB程序实现这一加密功能，程序界面和代码如下所示：

Private Sub Com_ jm_ Click()

    Dim x As String, ch As String, cl As String

    Dim sl As String, s2 As String, s As String

    Dim i As Integer, n As Integer, y As Integer

    x= Text1. Text

    n=Len(x)

    For i=1 To n

        ch= Mid(x, i, 1)

        If ch >= "0" And ch <= "9" Then

               ①    

            s2=s2 & y

        Elself ch >="a" And ch<="z" Then

            y=(Asc(ch)-Asc("a")+3)Mod 26

              ②   

            s1=c1+s1

        Else

            y=(Asc(ch)- Asc("A")+3) Mod 26

            c2=Chr(Asc("A")+y)

            s1=c2+s1

        End If

    Next i

      ③  

    Text2 Text=s

End sub