[weberr]

Is there a way to increment/decriment a value before replacing it?
I have a book structured with 90 chapters, each chapter a separate file; however, the chapter numbers are 38-90 (probably from using EpubSplit to break up a 'complete set'.
I would like to renumber the Chapters to be 1-90.
The chapter headings are easy to find: <h2 class="calibre1">Chapter ([0-9]+)</h2>
For replacement is there something akin to <h2 class="calibre1">Chapter \1-37</h2>