two instances of the same kernel version, different modules

[Cornelius Kölbel <cornelius koelbel gmx de>]

Hello,

I use one version of kernel sources but will compile different instances 
of the kernel and of the modules.
So I will have a module directory /lib/modules/2.4.20 and a 
module-directory /lib/modules/2.4.20-b belonging to the second compiled 
kernel.

How can I tell lilo that the second compiled kernel will find its 
modules in the directory /lib/modules/2.4.20-b.

I want to be able to boot either kernel

2.4.20
2.4.20-b

But also when I but the kernel 2.4.20-b the kernel looks for its modules 
in /lib/modules/2.4.20

Any hints?
Thanks
Cornelius