Generating models from a parent by entering a single integer

Hi there,
I was wanting this but could not be able to figure how to go about
it..
I am creating an application that includes batch details that includes
models called samples in it. Its a multi form and every thing is
being created by following Mr. Ryan.B 's tutorials. Now that I want
some Ajax to go about.
I required in my form, a field that asks how many samples do they have
per batch (one to many relation) and also
in the models batch.rb
i have has_many :samples
and
in the sample.rb
belongs_to :batch
Now once the user enters samples (for eg. 4, as an integer) ... the
form generates 4 fields for filling in information of the samples...
Is this possible by any means.. (it should be)..
Can any one help me with this... If suggestions like guides or books
or even tutorials would be wonderful, though Railcasts didnt have
this...
thanks in advance