No it is not possible to vary allocations in that way.
You have two pieces of data you can play with:
- A resource's max units (How much of their day they can work on the project)
- A resource's allocation (How much of their day they can be allocated to a specific task
You can prioritise one task over another, so that the allocated resources will attempt to finish it before lower priority tasks, before moving on to other tasks, but you cannot vary a resource's allocation to a task depending on what day it is.
You could split a task into multiple one-day chunks and vary a resource's allocation to those tasks, but the plan would quickly become a maintenance nightmare for anything more than a trivial number of tasks, particularly if those tasks started moving around in the plan.