3道简单的VB编程题目，谢谢各位帮忙解答~

1、求和
Private Sub Form_Click()
Dim rSum As Single
Dim i As Integer

For i = 1 To 100
If i Mod 2 = 0 Then
'偶数
rSum = rSum - 1 / i
Else
'奇数
rSum = rSum + 1 / i
End If
Next

Print rSum

End Sub

2、素数函数
Private Function IsPrime(iNum As Integer) As Boolean

IsPrime = False

'剔除1
If iNum = 1 Then Exit Function

'剔除除2以外的偶数
If iNum <> 2 Then
If iNum Mod 2 = 0 Then Exit Function
End If

'按素数定义检查(实际只需要试除根号iNum以下的数)
Dim i As Integer
For i = 3 To Sqr(iNum)
If iNum Mod i = 0 Then Exit Function
Next

IsPrime = True

End Function

3、统计
窗体上放一个按钮 cmdCount

Private sString As String

Private Sub cmdCount_Click()
Dim iNum As Integer, iLetter As Integer, iOther As Integer
Dim i As Integer, s As Variant

For i = 1 To Len(sString)
s = Mid(sString, i, 1)

If InStr("1234567890", s) <> 0 Then iNum = iNum + 1 '数字
If InStr("abcdefghijklmnopqrstuvwxyz", LCase(s)) <> 0 Then iLetter = iLetter + 1 '字母
Next

iOther = Len(sString) - iNum - iLetter

MsgBox "数字: " & iNum & vbCrLf & "字母: " & iLetter & vbCrLf & "其它: " & iOther

End Sub

Private Sub Form_Load()

sString = InputBox("请输入位数小于100的字符串")

'不符合条件则清空
If Len(sString) >= 100 Then
MsgBox "位数应小于100", vbExclamation
sString = ""
End If

End Sub

200分我给你做