Insert text from one line to another and delete source line

[Paulova]

<h2>Title
<h3>Source text1</h3>
<h4><a href="

http://url">

[qwerty]</a></h4>
<h3>Source text2</h3>
<h4><a href="

http://url">

[qwerty]</a></h4>
<h2>...
<h3>...
<h4>...
<h2>...
<h3>...
...
Trying to insert "Source text" (always is between <h3></h3> tags in "[qwerty]" (target to replace is always [qwerty] with brackets) and delete line that contain source text. Line containig "[qwerty]" is always the next to line containig "Source text". So desired ouput:
<h2>Title
<h4><a href="

http://url">Source

text1</a></h4>
<h4><a href="

http://url">Source

text2</a></h4>
<h2>Title
<h4>...
<h2>Title
...

I am so newbie to do this for now...

 

[PHV]

A starting point:
nawk '
/<h3>/{x=$0;sub(/.*<h3>/,"",x);sub(/<\/h3>.*/,"",x);next}
/[qwerty]/{sub(/\[qwerty\]/,x)}
1
' /path/to/input > output

Hope This Helps, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884 or FAQ222-2244