adding the same column of two diff rows to get new row

hi all,
i have a structure as shown below
--332a
--332b(shld get disabled wen the following child r visible,i got dis...)
--332b
--332c
--332d
--332e
--332f
--332f
--332g
--332h




the parent 332b's 9th column shld be the added value of respective three children's 9th column values....wen i perform this calculation...nt nly the parent 332b is getting updated...but even the child 332b is updated..i want nly 332b parent to be updated.....
plz
help