I'm not an expert when it comes to work with tables, and your post has actually motivated me to try to do some stuff with autolisp generated table objects after many years. I'm maybe completely wrong, but look this:
https://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/set-cell-style-via-lisp/m-p/7220177/...
You should reshape this code (which applies style "data" to all cells in table) so that it applies style "Title" to cells in first row, and "Header" to those in second row. You may also use what @CodeDing proposed but then add counters instead "2 0" in
(vla-setcellstyle (vlax-ename->vla-object (car (entsel))) 2 0 "Header")
If you modify existent table to a column then that function has to reapply this to that particular column. For anything more we would need more details or a sample.
Miljenko Hatlak

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