ResponseBodies Parameter with Slight Variances

How can I change one part of the $ref, or add to it?

I have an OpenAPI 3.x response body:

ordernumber:
  $ref: '#/components/requestBodies/ordernumber'

The descriptive text is applicable to every instance I use this in, except for the last line. That changes for each product, like a product number.

I'd guess it'd be like this, but of course, this doesn't work.

ordernumber:
  $ref: '#/components/requestBodies/ordernumber'
  description: For all units number T100-T1200.