Formatted search - Default WH

Hello,

I would like to create a formatted search on A/R invoice. I would like to insert a specific warehouse code into INV1.WhsCode field in document lines, when a specific sales employee is selected on the document window. When any other sales employee is selected, then I would liketo use the default warehouse for the Item in the document line (OITM.DfltWH)

I have started and tried with versions of this query, but didn't succeeded yet:

SELECT CASE WHEN ($[OINV.SlpCode]=1) THEN 'A1' ELSE OITM.DfltWH FROM OITM END

Could you help me please, it must be some basic syntax problem 😊

Thank you,

All the best,

Balazs