Is there a mechanism that one can use to wrap conditional php logic around the substitution strings that are offered in the header section?

For example:

<?php if(is_front_page()) { echo '%bar1'; } ?>

I'm trying to leverage the benefits of the substitution strings but wrap them around page specific criteria. This piece of code does not seem to work.

For now, I've grabbed the source html from the rendered page and put it in for %bar1.

<?php if(is_front_page()) { echo '<div class="horbar1">&nbsp;</div>'; } ?>

No, but you could use CSS to deal with it

.horbar1 {display:none !important;}
body.home .horbar1 {display:block  !important;}