You cannot set two triggers for the insert through the wizard, you would need to modify the code after it is created to add the second condition to the trigger if statement.
for example the trigger code for any form post would look like this:
if($_SERVER["REQUEST_METHOD"] == "POST"){
to add a condition for the recordset being empty, change that to:
if($_SERVER["REQUEST_METHOD"] == "POST" && ($totalRows_RecordsetName == 0)){