Enter "99999" where there is blank in conversion file for SAP BPC 10.0 (NW)

Hello Experts,

I am working on legal consolidation. While uploading transaction data from BW, there are few fields which are blank for a table:

For eg: In case of cost of sales approach, for balance sheet items there is no functional area. Hence the field is blank.

I want to add "999" to Balance sheet items in 0FUNCAREA at the time of uploading TRANSACTION DATA.

Since my system is showing an error for blank fields, Can anyone of you help me on how my conversion file will look like.

Any help on this will be highly appreciated.

thanks