SAP BPC 10.1 Characteristics derivation using Exit

[n_kukunur]

Hi,

I am trying to derive Username and date using Characteristic derivations in BPC 10.1, I am able to populate both but the issue is all the dataset from the A40 is getting overwritten with new values even though user doesn't modify all the records in that planning layout. for below example dataset.

Revenue CC1 1000 USER1 10/12/2019 ,

Sales CC1 500 USER1 10/12/2019.

If the User2 Modifies Sales line, only Sales should be updated with User2 but both Revenue and Sales are getting updated with User2. is this how it should work ??

Code is very simple like below.

ASSIGN COMPONENT 'BPCUSER' OF STRUCTURE C_S_CHAS to <USER1>.
IF sy-subrc = 0.

IF sy-uname = 'BWREMOTE'.
<USER1> = ' '.
ELSE.
<USER1> = sy-uname.
ENDIF.
ENDIF.

Please let me know what i am missing here.

thanks

Vijay