MS Project: how to make a task with a hard binding of start and end?

Question

Microsoft Office

I have task A with a specific start date.
I have task B with a specific due date.
How to create a task C that starts exactly n days after the start of task A and ends exactly m days before the end of task B (that is, the duration of task C is a variable).
HH bindings for tasks A and C and HO bindings for tasks B and C do not give the desired result.