Want to add a +1 and -1 button to admin product page

I am after some help trying to modify the Category/Product page in admin.

On the page you can click a product to edit, change the status etc however sometimes when I get some addition stock in I would like to be able to just click a button to add 1 stock item or if I have found 1 damaged etc subtract 1 stock item.

Currently I have to go into each individual item and manually change the qty, I figure it shouldnt be too hard on the category/product list page that next to the status on/off buttons to add a +1/-1 button so that I just have to click this button to update the qty without entering the item each time.

Any ideas or suggestion?

I believe it is the admin/catagories.php page that I need to modify to achieve this.