CELL reference removed in BPC reporting, showing #REF!

I am creating a BPC report, trying to get data in a data worksheet, then add excel formula to refer to the data sheet.

e.g. in data_sheet!F202, I have data

so in the same workbook, the report sheet somewhere G77 I input "=data_sheet!F202". it worked fine untile I expand my BPC report,

then CELL G77 shows #REF!.

I am wondering how can I have my reference unaffected by the BPC expansion.

this sounds pretty basic issue, however I need your help as I can't figure it out.

I think before range/after range do work, but my reporting is more complex than the before range/after range can handle.

please advise.

George