Is there an interactive countdown plugin?

Hey-

My mom wants to collect canned goods for a local charity on their website. She wants to have like “500 more cans needed” each month and each time someone pledges to donate (doesn’t actually need to pay, just SAYS they’ll bring the food), the counter goes down. Any ideas? Also, does anyone know a way that ISN’T a WP plugin because their new site might not end up being WP.

Thanks!