一道程序设计题

下面VB程序的功能是:计算表达式1+1/3+1/5+...+1/99的值,并在文本框TEXT1中输出该表达式的值.为了实现这一功能,程序中划线处的语句应更正为:---------

private sub command1-click()
dim sum as single ,i as integer
sum =0
for i = 1 to 99 step2
sum = sum + i
next i
text1.text = str(sum)
end sub

划线处为sum = sum + i

sum = sum + 1 / i 正确

+=运算符是C/C++的运算符，怎能用在VB上哈？！