Need help with a table problem: style setting on very last line of a table split over pages

I'm sure the docs have an answer to this question but I haven't been 
able to find it.

I have a report with several tables. Some tables have a total row at the 
bottom, that I would like to be highlighted differently. Others don't. 
For the table with a total row I specify the highlight colour like this:

TotaltableStyle = TableStyle([
                             ('ROWBACKGROUNDS',  (0,-1), (-1,-1), 
[NibcLightBlue[20]]),
                             ('TEXTCOLOR',       (0,-1), (-1,-1), black)
                             ],
                             parent=DealtableStyle)

The parent here is of course the style for tables that don't have a 
total row at the bottom. This works perfectly ... unless the table is 
split over multiple pages. Then, I get this highlighting on the last row 
on every page, when what I want to highlight is the last row on the last 
page.

An earlier version of this program solved the problem using two tables, 
one for the detail, with a single-row table below it for the totals. But 
that version specified the column widths explicitly, so the two tables 
matched up. But now the tables are more crowded, and I don't have the 
luxury of giving each column enough width to accommodate the longest 
data item over all of the tables. So, I really need the detail table to 
calculate its own column widths , and having two different tables means 
that the column widths are computed independently and, of course, do not 
match.

So, either I need to copy the column widths from the detail table to the 
total table; or I need to specify a style that applies only to the very 
last line of the table. I haven't found a way to do either. I suspect 
that indicates I'm looking for the answer to the wrong question.

In any case, I can't imagine I'm the only person who has ever wanted to 
do this.

So, what is the proper way to apply a different style only to the very 
last logical line of a table, even if it is split over multiple pages 
and so has more than one physical last line?