php in cmsb text field

I want to put some php in a text field that will work at runtime. Basically I have an includes file containing meta tags, and the title and description tag are pulled in from the meta tag table in cmsb. However there are certain instances where I want to pull in the news story title as the meta title instead of just some keyed text.

for instance
the meta tag include file contains stuff like this


if ($meta_page =='news') {
$title=$meta_tagsRecord['news_title'];
$description=$meta_tagsRecord['news_description'] ;
}

and I want to put in cmsb text field for meta_tags news title something like
<?php echo $newsDRecord['heading'] ?/>

but instead of printing the result it just shows <?php echo $newsDRecord['heading'] ?/> as text, which is not the desired result.

any ideas or confused as to what I am trying to do, please respond either way... thanks