Trying to figure out what CRM or website to use for a custom client portal

I’m currently using honeybook but they don’t seem to be equipped with my needs. I need a client portal where the client can see a calendar that is specific to them. They can add important dates. For example if they go to add a new date a form will pop up for them to fill out. Almost like stating a “new project”

It’s similar to what sprout social and later.com do for planning and publishing social media content, except I just need it so they can submit new projects and add info from a calendar view.

Anyone have ideas on the best way to integrate this? Currently have a Squarespace website but happy to change if the client portal isn’t compatible.