How to add a custom blogger post title

few days ago I changed my blogger tittle code
<title><data:blog.pageTitle/></title>

to following code

<!-- Start Widget-based: Changing the Blogger Title Tag -->
<b:if cond='data:blog.pageType == &quot;index&quot;'>
<title><data:blog.title/></title>
<b:else/>
<title><data:blog.pageName/></title>
</b:if>
<!-- End Widget-based: Changing the Blogger Title Tag -->

but now my blog post name is my blog post title.


I want to change my blog post title to custom title, instead of my blog post name


any ideas how to do this??????????