下面程序的功能是：计算表达式1+3+5+…+(2n-1)的值，在文本框Text1中输入n的值，结果在文本框Text2中输出。则程序中划线处的语句应填____________。
Private Sub Command1_Click()
Dim sum As Long,i As Integer,n As Integer
sum = 0
n = Val(Text1.Text)
For i =" 1" To 2 * n - 1 Step 2
             
Next i
Text2.Text=Str(sum)
End Sub