How to define a linear distributed moment along with the tube

[xiazhn]

The moment load can be applied only to the sigle node or node set as a concentrated load, but the magnitude of it changed along with the tube. I tried with user subroutine, but it is only valid in applying the distributed element-based or surface-based load.
Maybe *AMPLITUDE is the way to solve my problem, and I checked the documentation, but I could find no tips for my case but that with respect to time.

What else can I try to adding the moment into the model?

Thanks for your suggestion.