RPM Package question

Hi,
I have built one RPM last year. now we have another version of that RPM. in previous release we had few extra files then now. so when user upgrade it those files get deleted by RPM package. We want to retain those files.

now for workaround i thought of backing up those file during "Preinstall" section and restore in "post install" but that too doesn't work because RPM package has that functionality to compare files and delete them even after "post install".

i am sure people has encountered this issue and have fix i have one more workaround and that worked but i was wondering if there is anything simpler way to do this using functionality of RPM.

Its now urgent foe me.
Thanks, Ajay