How to read structure field in absl?

[63abapdeveloper]

Hello,

in my bo I defined a structure field and read AccountID from a PuplicOutport. 

I want to write EC_BusinessPartnerID_IN automatically in the field partner.

I tried it with aftermodify, but in this. there is no field for Structure.

Thats a new EC on BP. I want to fill column partner automatically with the partnernumber.

Thanks