I need to check a table field and if it is "N" I have to run an application

Hi all,

I got a table to monitor and when a field table (shortly a new records is inserted) is equal to ‘N’ I’ve to sc_redir to an application that print it .
After that I set that record field to ‘Y’.

How can I do this checking for instance every 30 seconds if there are new records created on the table ??
Is it better to use a control application ?