How to paginate a table using a relation with other table

Hello,

   I have this model

   Item
     has_many :tasks

   Task
     belongs_to :item

    I have a filter

   @task_pages, @tasks =paginate :tasks, :per_page => 10, :conditions
=> ["company_id = ?', company_id]

    How can I use a set of Items to return some records in Tasks, and
use it in Paginate?

     Item.find (:all, :conditions => ['model = ?','KJ-393'])

     and paginate just the tasks thar belongs to this Items?

Thank you