Force sold out product to the last page

[pczibor]

Hello guys,

I am facing a strange problem hoping you guys can give me a solution.

In a nutshell:

I have like 9 pages on my products page. My problem is that there are some products which are sold out and there is a ribbon over the product image. When I sort the products by stock, well it seems to be sorted correctly - product with 0 value in stock are on the last page but the products which are sold out, and the option to forbind ordering is chcecked are ordered kind of randomly.

some of them are on the first page and some of them are somwehere between page 1 - 7 but none of them is on page 9(which is the last one).

What i wanna do, is to force all products which are sold out to the very last page so the page 8 - 9 will contain only sold out products. 

has anybody faced this problem or is there a solution for this??

PS I think I once came across a module which solves this problem but right now I'd rather find a solution for which I don't have to pay. I know some basics of PHP and OOP and I even found the script in product-sort.tpl and front-controller.tpl but I am not realy sure where I should make the changes and how.

thanks for help in advance!