Compile mISDN for B400P

hello, all of users:
I want to compile mISDN and asterisk. but i get the msr.c error during compiling kernel. i check that, under the arch/kernel, there is no such file. i am using centos 5 to install that and also follow the material from asteriskguru:http://www.asteriskguru.com/tutorials/chan_misdn.html
and misdn.org/index.php/Installing_mISDN. but the two links are not very clear. i am still struggleing with that. please give me a hint for centos 5. thanks
zhu8080