Recording negative volumes for positive dollar amounts

[KB9]

Hello all,

We are trying to interface one system with S4 Hana, and one of the GL entries required to be posted is positive purchases with negative dollar amounts to the same GL account, how do we incorporate that?  

Do you suggest any kind of rule needs to be introduced in the interface for reading the data or do you think that separate STAT account should be created? Your wisdom and response is valued and appreciated.

Thanks,