Arithmetic operation with numbers inside xml tags of the same name?

Question

XML

There is a large xml document, you need to take all the numbers inside the tags of the same name, perform an arithmetic operation with them, return them back, do not touch the rest.
That is, for example, divide all the numbers inside by two. Notepad++ macros cannot do arithmetic, and js I'm afraid that it will spoil the rest of the content after converting to an array and back. What other options are there?
<a> <b>100</b><b>200</b><b>300</b> </a>
<b></b>

Answer 1

I would work with xml as with dom and not regular expressions.