How to add a Smarty into url('') on a CSS file

Hi,

Before I break my pc, I'd like to ask, is it possible to add a Smarty to Background-img url('') on a CSS file?

I have something that looks like:

#cart_block h4 { background-image: url('../../../img/block_header_exclusive_cart.png') ; }

HTML:

I need to add Smarty:

{'lang_iso'}

HTML:

So it'd look like:

#cart_block h4 { background-image: url('../../../img/block_header_exclusive_cart_en.png') ; }

HTML:

When the English language is selected for example.

I need the 2 last letter to change with the language.
This doesn't work:

#cart_block h4 { background-image: url('../../../img/block_header_exclusive_cart_{'lang_iso'}.png') ; }

HTML:

Thank you.