Changing warning message to error message - Entry Sheet

Hi everyone,

When I try to cancel an entry sheet that already has an invoice, the system shows me the following message: Message 11388 - "An invoice already exists for this entry sheet"

This message in your system is only an warning system, but I'd like to turn it an error message, how can I do that?

I tried go to SPRO --> Materials Management --> Purchasing --> Environment Data --> Define Attributes of System Messages --> System Messages

But I didn't find there the me message mentioned above.

Thanks in advance.

Best Regards,

Rodrigo Amorim