Display products in views ordered by "in_stock".

The problem is product qty is dynamic value calculating like this:
[code]
$stocklevel = uc_stock_level($node->model);
[/code]
but there are no fields like $node->is_in_stock, $node->stock_level
but it will be very useful to use them in views.

I've tried to solve it using CCK dynamic_field (it computes its value in runtime).
But views uses sql query to database, so dynamic fields can be used to sort data:
http://drupal.org/node/424538