Currently using vanilla Odoo 16 Enterprise online.

Our Sales Orders typically have several straight forward milestones that are invoices on completion.  No problem there.

As we progress through project milestones, our clients will routinely have details that come up.  These change the scope of work and would normally result in a change order. 

To avoid the lengthy change order process, in every Sales Order we include a negotiated "not-to-exceed" allowance (or budget line item) we call "Project Support".  The client allows us to invoice time and materials against Project Support whenever a small scope change occurs.  We need to keep track of how much we bill against "Project Support".

The problem I am having is that I can't figure out how to create the a "Project Support" product what will allow any of 6 different employees (each with a different "sales price"). 

Here is an example of how we use it:  

Project ABC has a Project Support budget of $5000.  

Surprise Task 1 occurs and the client approves us to use the Project Support allowance. - Bill works on this task for 10hrs and his charge rate is $100.  Joe works on the same task for 5hrs and his rate is $200.  We deliver the work and create an itemized invoice.  

Surprise Task 2 occurs. We inform the client he has $3000 left in his Project Support allowance and believe it will cost under $3000.  The client approves the new work and three different employees get to work.  Bill has 10hrs @ $100/hr, Joe works 5hrs @ $200/hr and Adam works 10hrs @ $150/hr..  We deliver the work and deliver an itemized invoice.

I have come up with a couple work arounds but they are not optimal.

Any ideas how to make Odoo work this way without custom code?

Thank you in advance!