Meta titles & meta descriptions placeholder -- 2

1 category, for example 'HP 200 series' can be linked under 4 different main categories. For example under 'HP laptop battery' and also under 'HP laptop adapter'. But the category 'HP 200 series' can only contain 1 meta title and 1 meta description. I can edit in the backend with opencart. But I want a different meta titles and meta desciptions if it's linked under a different category. For example the meta title for HP 200 Series should be like this (depending on the main category): Home > HP Accu > Hp 200 Series should have a meta title like: "Buy your HP 200 series laptop [battery] in our webshop." Home > HP Adapter > Hp 200 Series should have a meta title like: "Buy your HP 200 series laptop [adapter] in our webshop." I guess the best and most efficient solution (preferably without making any database changes) would be to use a placeholder in the meta description, like this: "Buy your HP 200 series laptop [placeholder] in our webshop." And when the this page loads: [login to view URL] then this placeholder be injected with the the main category short name "adapter". So the solution would be like this that in the meta titles and description I can use a placeholder like this [placeholder-main-cat-name]. If I don't use a placeholder in the meta title or description then it just needs to behave normal, like it does now.