How can I setup the CRM so whenever the Amount field is being changed, the user who changes it needs to fill in a reason of change -> Could be a Subform entry or even a note.

I'm happy to use any of available features -> Workflows, Functions, Buttons, Blueprint, Whatever works.

It would be usefull when lets say we have a deal of 30 000 on the contract and during the fullfilment we need to adjust the amount to 33000. If someone changes it -> Id like to enforce the user to write down what is the reason of contract value change.