Resource Planning

I would like to set up a resource planner that allows me to track the following:

project start date, project end date
resources allocated to the project for specific periods of time during the lifespan of the project (start date end dates)
resources could be allocated to one or more projects for various time periods within the lifespan of the project. (their role is the task they will be undertaking e.g project manager, contracts manager, design manager)
during a planning period, e.g defined by start date and end date I would like to be able to see if I have resource availability during this planned period so i can reallocate to another project if so required).

I have looked at the resource planning base https://airtable.com/universe/expcKQVYLmFG3RF1l/resource-planning. However resource is allocated to project by % time and availability then is dependant on end date of a project as opposed to any date within the planning period.

If I have an allocation start date and end date to multiple projects for a resources, how can i configure a formula that will calculate their availability during an inputted planning period.

I hope the above is clear and i really appreciate any help on offer.

Regards