【例一】用文本框输入n值，单击命令按钮求S=4×(1-1/3+1/5-1/7+1/9-…+(-1)n+1×(1/(2n-1)))，结果显示于标签中。
程序运行效果如下图所示：
程序源码：
Option Explicit
Private Sub Command1_Click()
Dim S As Single, n As Integer
S = 0
n = Val(Text1.Text)
If n > 0 Then
For n = 1 To n
S = S + ((-1) ^ (n + 1)) * (1 / (2 * n - 1))
Next n
ElseIf n = 0 Then
S = 1
ElseIf n < 0 Then
For n = -1 To n Step -1
S = S + ((-1) ^ (n + 1)) * (1 / (2 * n - 1))
Next n
End If
S = 4 * S
Label2.Caption = S
End Sub
【例二】有一分数序列2/1,3/2,5/3,8/5,…，单击窗体求出这个数列的前20项的和。结果显示于窗体上。
分析：分数序列中后一项的分母是前一项的分子；分数序列中后一项的分子是前一项分数的分子与分母之和。
程序源码如下：
Option Explicit
Private Sub Form_Click()
Dim FenMu As Integer, FenZi As Integer, FenMu1 As Integer
Dim I As Integer, Sum As Single
FenMu = 1: FenZi = 2: Sum = 0
For I = 1 To 20
FenMu1 = FenZi ' 保存前一项分数的分子，以作为后一项分数的分母
Sum = Sum + FenZi / FenMu
FenZi = FenMu + FenZi
FenMu = FenMu1
Next I
Print Sum
End Sub
运行结果：
32.66026
【例三】单击窗体时求的值，结果显示于窗体上。
程序代码如下：
Option Explicit
Private Sub Form_Click()
Dim K As Integer, Sum As Single
Sum = 0
For K = 1 To 100
Sum = Sum + K
Next K
For K = 1 To 50
Sum = Sum + K * K
Next K
For K = 1 To 10
Sum = Sum + 1 / K
Next K
Print Sum ' 在窗体上显示结果
End Sub
运行结果：
47977.93