How to block requests to Translator service based on number of characters in the source document?

Question

I'm working on a project that utilizes Microsoft Azure's AI Translator service to translate documents in various formats. Specifically, I'm using the batch translation API.

The problem:

The Translator service pricing is based on number of characters in translated document. And the number of characters is knows only after the document was processed by the service.

I would like to control the the amount of characters processed by the service and maybe stop the execution if the character count is above a threshold.

Is there any solution out there in Azure's landscape that can help me? I would like to avoid creating a custom service to count characters , for various file types supported by AI Translator

So far, I read the services documentation and searched the internet...Alas, it seems people just write their own code to count teh characters.