Methods for stepping through results?

Greetings,

Is there any way to do the following:

1.  Return a query in groups of x (i.e. 10 or 20) and progressively return
result groups of x.  Just think of search engine navigation.

2.  I have a client who wants to be able to select certain rows (tuples) of
a result and then "re-submit" the query and have only those rows selected
in the new results.  For example, if a query returns 10 rows and rows
2,4,7,9 are checked, when re-submitted only rows 2,4,7,9 would be returned.
 I know it is kind of stupid, but I have to please the customer :(

The interface I'm using is libpq, apache server, and Netscape/IE.

Thanks,
Matthew