[ZPT] Nesting a Tag in CSS

[beno]

Hi;
How would I accomplish the following in a way that will perform the 
substitution that I want?

<style type="text/css">
  .headline { position: absolute;
    top: <p tal:content="python:here.sizeCalc2(50,here.size(None, here))"/>;
    }
</style>

If I place this:
<p tal:content="python:here.sizeCalc2(50,here.size(None, here))"/>
in the body of the page, it renders a numerical value (say, *40*). How can 
I get that to happen nested in a style declaration?
TIA,
beno