翻译成英文：“顺便说一句，昨天MSN已经与你沟通过...”

楼主的意思不太明确
如果你的意思是“昨天我在MSN上已经和你沟通过...”的话,不妨这么翻译：
By the way, like I told you through MSN,the CC program has been updated very lately,so I have downloaded it.

By the way, MSN had already communicated with you at yesterday: CC procedure has been newer newly too, so I have been already download

By the way, we had chatted on MSN yesterday that CC programe have been uploaded to the newest version,also i had already downloaded it.

不知道CC是什么?

顺便说一句，昨天MSN已经与你沟通过：
By the way, I contacted you on MSN yesterday:

CC程序也是最新更新过的，所以我也已经下载了
I have downloaded the most updated CC program.

这样就可以了，楼主的话也没什么歧义

by the way,I have communicate with you by MSN:the CC program is the newest version,so I have download it

by the way, i had talked with you on MSN yesterday. the CC program is latest updated so i have downloaded it.