Search for a tag inside a tag that has a class

Yet another search related question from me, once again using Dreamweaver 2015;

So one of the ways the HTML documents I'm working on is basically broken is there's a disgustingly shockingly large number of structural tables, all of them completely broken in their code. (It's so bad I routinely just strip all the <col> and <tbody> tags and re-build them later because they're ALL incorrectly applied and have a couple of saved searches set up to add in missing <tr> tags...yes, it's that bad)

One thing I'd like to be able to fix is automating the correction of the header cells in the assigned header columns and rows. The "header columns" is actually fairly easy to fix, each <td> is assigned the "tablelables2" class (no, I didn't come up with these class names), so simply doing a search for all <td> tags with class="tablelables2" and replacing them with <th> tags works just fine.

It's the header rows that the problem occurs. There's two header rows (I know, I know, that's the WRONG way to do it, but again, I'm just fixing things up as best I'm allowed), and both have classes assigned on the row, not the cells, so my solution that I'm using for the header columns won't work here.

Is there a way to tell Dreamweaver "Find all <td> tags inside only the <tr> tags with the attribute 'class="tablelables"' and replace them with <th> tags"?