有 Click 事件对应的程序如下：
Private Sub Commandl_Click()
Dim sum As Double, x As Double
sum=0
n=0
For i=1 To 5
x=n/1
n=n+1
sum=sum+x
Next i
End Sub
该程序通过 For 循环计算一个表达式的值， 该表达式是