adding another parameter when posting

[emath]

these are the hooks which thank_you mod use :

cache_templates
userdata_delete
showpost_complete
showthread_complete
template_groups
threaddata_delete
postdata_delete
postbit_display_start
postbit_display_complete
global_setup_complete
member_profileblock_fetch_unwrapped
userdata_update_username

in which one shall i put in the $validvariables my fields ?

and again ,
where my table ive created for this goes in all this story ?

thanks,