用VB编一个程序

用输入框输入一个数n，若此数是大于0的正整数，则求S=1 - 2/3 + 4/5 - ……2n/2n+1，否则要求重新输入数据，直到数据合理为止。

楼上 问问1队 团队的答案是错的。下面的代码是按题目的要求写的，如有疑问请追问。

Private Sub Command1_Click()
Dim n As Double
Dim s As Double
Dim f As Integer
Dim i As Integer
Do
n = Val(InputBox("输入N:"))
If n > 0 And Int(n) = n Then
Exit Do
Else
MsgBox "请输入正整数!"
End If
Loop While True
s = 1
f = -1
For i = 1 To n
s = s + f * 2 * i / (2 * i + 1)
f = -f
Next
MsgBox "S=" & s
End Sub

Dim sum As Double, k As Double Dim n As Double Dim i As Integer n = CInt(InputBox("请输入n:"))

if n>0 and n=int(n) then k = 1 sum = 0 For i = 1 To n sum = sum + k / (2 * i - 1) k = -k Next i msgbox "sum = " sum

else

msgbox"请输入正整数",vbokonly

end if

这样就可以了