Module to add "Sale" tag on product listings
 

I´m trying to create a module to add an "On Sale" graphical tag similar to the one displayed when the product has a sale price in listings (as when using the wholesale module), but we need to do it based on a global attribute which will set some products flagged as "On sale". The question is: How can I retrieve this attribute value from the DB so as to apply this tag when the product is "on sale" on the product´s Tpls ?

Thanks !

(X-Cart 5.2.15)