BPC NW10 - data collection - manage the flow of intercompanies

Hi,

For the budgeting process, there are 2 budget form
First input Form 1: enter the total amount of balance (ignoring the flow intercompanies)
ENTITY	ACCOUNT	INTERCO	MEASURES
Company1	Acount 1	NO_INTERCO	100
Second input Form 2: enter the flow inter companies
ENTITY	ACCOUNT	INTERCO	MEASURES
Company1	Acount 1	Company2	20
In summary, unfortunately the data records are
ENTITY	ACCOUNT	INTERCO	MEASURES
Company1	Acount 1	NO_INTERCO	100
Company1	Acount 1	Company2	20
Target : when saving data of flux intercompanies Form 2, the system automatically reduces the values 'no_intercos'
ENTITY	ACCOUNT	INTERCO	MEASURES
Company1	Acount 1	NO_INTERCO	80
Company1	Acount 1	Company2	20
We created the excel formula on the record 'No_interco ' = sum of flow intercompanies - total amount = 100-20 =80
But after save data, the excel formula disappears
We changed the sheet options / refresh : we select the following options
Keep formula on data
Keep formulas static that reference report cells
But after save data, the excel formula always disappears
Do you have the solution for reduction the values 'no_intercos' to 80? Bastien