How to create formula to count upcoming tasks in the next 90 days?

I want to see how many tasks each project I have are upcoming in the next 90 days. I can run a report to see this information, but I want to be able to display it in an easy to read chart with each project showing how many tasks they have. See attached example.

I built the attached chart by running the report with the filters "start date in 90 days" and just counted how many tasks were in each project and then manually keyed the amount in to my project roll up sheet. From there I created a chart for my dashboard.

However, I want to figure out a way to automate this with a formula so you do not need to manually count each tasks for the projects. There's about 6 different projects each with their own sheet. I know you can't reference a report for a formula. What are my other options?