alv sorting

hi

need to sort alv data, but the entries are like header and item

means first line is of header data and if has items then

the items will be displayed starting from second line but some columns for all items

will be empty (means header data at the top line refers)

now second header data comes and then its items.

in such case how to sort the ALV basing on the header number.

while sorting all the items are going at the bottom since it has no header number in its line

and header items are coming at the top

how to sort these entries correctly