>what can I do to show values (many rows) and totals in the last row?

Here, you should change your grid.recordsource. You will use cursor here:
Select 1 as gridorder,myfield1,myfield2 From mytable Where parentid=... Into Cursor mycursor Order by 1 ;
Union All Select 2 as gridorder,Sum(myfield1) As myfield1 ... From mytable Where parentid=...

Now whole cursor will be shown in your grid.