apt-get can not find debian package in cdrom

[Ravi Roy <ravi.aroy@gmail.com>]

Hi,

I'm using debian 6.0 Squeeze for my product and its installation is
headless using preseed. I have a strange issue that CD contains a
debian package but after mounting the cdrom when I try to install the
package it says :

$ sudo apt-get install mypackage
Reading package lists .. Done
Building dependency tree
Reading state information .. Done
Package mypackage is not available, but it is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'mypackage' has not installation candidate.

I verfied it and it is available in cdrom; I'm using apt and apt-utils
versions 0.8.10.3.
It would be helpful if somebody can point to a direction which may
help to resolve this issue.

Thanks you!

Regards
Ravi.