I think the word you are looking for is: 对了， as an interjection while speaking. for example: oh, by the way, where are my sunglasses? 哦，对了，我的太阳镜在哪儿呢？ Hope this is what your where looking for

顺便说一下shun4 bian4 shuo1 yi1 xia4 还有。。。hai4 you3 顺便问一下shun4 bian4 wen4 yi1 xia4+a question

by the way 有2个意思。the first meaning is“ 顺便问一下”，“顺便说一下“(这是个非常礼貌的说法），it is seldom used amony acquaintance...你也可以翻译成“另外”“还有”。。。.the second meaning is “在路上”。。。呵呵They fell out by the way. 他们在路上就争吵起来了。 字典上说的

Hi....shun4 bian4 shuo1 yi1 xia4 (顺便说一下）！ By the way, may I correct your sentence? You should say: by the way 用英文怎么说！ Hope this helps!

By the way = 顺便说一下 or 顺便说一句 ^^