Inputting and calculation prices in input forms

Dear experts,

We are migration a solution from BOC Standard to BPC Embedded (BW 7.5 on HANA).

I need to develop an input form that allows inputting prices when users select base level entity (top section on the picture). In the same input form. When users select parent (node) entity, then prices cannot be aggregated and have to be calculated on the fly as mEuro / kTons * 1000.

How can I design a BEX-query and/or Analysis workbook to achieve this?

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Best regards,

Oleksandr