Adding form fields dynamically

Hello

 How would I go about adding form fields dynamically? Here's what I'm trying to do.

 Before the form is created, I'll get a value from the querystring. This value is between 1 and 10. That number represents the number of times I should display a block of input fields in my form.

Example  of a blocks :

User #1
  Name:
  Age:

 User #2
  Name:
  Age:

 My actuall blocks are more complicated than those.

Is there a nice, clean way to do that? For example, using user controls or seomthing? I'll have to assign unic IDs to each fields...

I don't need the code, just the idea of how to go about doing that.

 Thanks
...