BOM table linking sketch part

I made one assembly drawing.which is showing parts in BOM table.These parts are having some sequence according to me.If I change the sequence of parts in table, the baloon serial no will be updated itself.  I sketch some part in assembly & add a row in BOM to show the baloon sequence. If now I want to change the sequence of parts in table the baloon serial no will not be updated itself. how can it be done

SolidworksBill Of Materials