In queries with two structures, a cell arises from the intersection of two structural elements. You can overwrite this implicit cell definition with an explicit one.
This chapter described functions, enhancements and changes that apply as of BW back end version 7.4 SPS12 / 7.5 SPS00.
On the Cells tab, you can specify whether a cell is used as an exception cell or help cell.
Note that using exception cells can have a negative impact on performance when you execute your query.