请教一道VB的题目

Private Sub Command1_Click()
Dim s1$, s2$, j1%, j2%

s1 = InputBox("请输入第1个字符!")
s2 = InputBox("请输入第2个字符!")

If s1 = "" Or s2 = "" Then Exit Sub

j1 = Asc(s1)
j2 = Asc(s2)

Print IIf((j1 - j2) Mod 2 <> 0, Chr(j1 + 1) & Chr(j2 + 1), Chr(j1 - 1) & Chr(j2 - 1))

End Sub

没看懂

Private Sub Command1_Click()
Dim str As String
Dim char1 As String, char2 As String, temp As String
str = InputBox("请输入两个字符")
If Len(str) = 2 Then
char1 = Left(str, 1)
char2 = Right(str, 1)
If Asc(char1) > Asc(char2) Then
temp = char1
char1 = char2
char2 = temp
End If
If (Asc(char2) - Asc(char1)) Mod 2 = 1 Then
MsgBox str & "的两个字符ASC码差为奇数，它们的后继字符为：" & Chr(Asc(char2) + 1)
Else
Ms