[texhax] How can I copy all contents in \box255?

[Chakrit Nimmanant]

Hi,
        I use "lineno" package in my book and it works well. However, If I can get all contents from \box255 before it will be \unvbox at every line by the output routine, I will surely improve my book series.
 
        At first , I tried to copy the box's contents into a token register, but it didn't work. 

        So, could you please suggest me how to get that contents from \box255
before \unvbox will blow all of my contents to vertical list by output routine in "lineno" package.

        Thanks a lot in advance for your kind suggestion.

Regards,
Rahagadhi Yamanag