how to excel formula in EVDRE report

Hi,

We are on bpc version 7.5, I am developing report that has material hierarchy than two columns that are picking budget and actual sale. Fourth column is variance of actual and budget that I am using excel formula as budget-actual. Now problem is when I expand the report this excel formula column get vanished (I have mapped a column key), I have hierarchy that user want to change so I can't make it a static report.

Material Hierarchy                    budget sale               Actual Sale          Variance

  xyz                                            100                           80                        20

Please suggest.

regards,

ray