msa50-workbench: how to set field sort1 from field sortl ?

Hello forum,

in tile bp -> details, I've mapped ctrlSortfieldT to BO Attribute Sortl.

So i can see the sortfield in bp-details.

But in order to exchange this mandatory-field with crm-online/r3,

I have to fill field sort1 in msa.

How can I set this field while updating the bp-detail dataset ?

Has anybody an idea esp. coding ?

Best regards

Gerd