That can be done in your recordset. You have to save a session variable to record the user's choice of how many records and give it a default value of however many records you want displayed at first. Then use that session variable in the recordset code in place of the number of rows to display. It would look something like:
$Recordset1 = new WA_MySQLi_RS("Recordset1",$pubsitepro_site,$_SESSION["RecordsToDisplay"]);