如何用vb编写1-2+3-4+5……+（-1）^(n+1)n的值n由自己指定

'楼上错了
Option Explicit
Dim A As Integer, i As Integer
Dim n As Integer
Dim St As String
Private Sub Form_Load()
Form1.AutoRedraw = True
St = InputBox("n=(n>0,n<1退出)", "输入", "0")
If St = "" Then Exit Sub
n = Int(Val(St))
If n < 1 Then Exit Sub
A = 0
For i = 1 To n
A = A + (-1) ^ (i + 1) * i
Next
Print "结果是："; A
End Sub

n=val(inputbox("请输入N的值："))
s=0
for i=1 to n
s=s+n*(-1)^(n+1)
next i
print s

你不妨用一个函数吧
private function sum_dou(n as integer) as double
dim sum as double
dim i as integer
sum=0
for i=1 to n
sum=sum+sum*(-1)^(i+1)
next i
sum_dou=sum
end function
直接用文本格式编写的，可能会有一些拼写错误，你自己稍微改一下，应该没有问题