applications linking

Hi ,

My requirement is , i have two applications , one is customer and second one is customer notes. i have to
add customer notes from customer app. link has to be given , from customer app to customer notes . when user selects a link , new popup has to come(customer notes) , in that pop up user has to add one more record. in that popup , only customer related old records should be there , and there should be a provision to add new records.can u plz give me the steps one by one.

Regards,
Hanumanth.