Invoice number chnages

Hi Experts,

In my current project, it is required to have one invoice number range for a rate category. Say for example, for rate category R1, invoice number range should be starting from "8", for rest of the rate category it will be starting from "7".

In the current system all the number ranges are starting with "7". I have made new number range starting with "8". I have not assigned that to any document type.

Can you please tell me if any events/exit/badi/enhancement spot available to write the above logic?

Or can anyone suggest any other way to meet the requirement?

Regards,

Bodhayan