Roll up count of child accounts

Hi,

I have a custom field on an account object named "Account Status", which tells me where the account is in their customer journey e.g. Onboarding, Live, Expansion, Churned etc.

For every parent account we will have multiple child accounts and what I would like to do is create a field on the account page that shows the count of related child accounts that have a status of Live and Expansion (there may be more statuses, but two is good for the example).

This will enable me to see the whitespace within a customer e.g. The customer has 200 locations, but we're only live in 50 of them.

I'm not sure I can do this with a straight roll up summary, and I've played around with creating a field on each individual account that can then be summed in a roll up on the parent, but I'm not coming up with anything that seems to work.

Any answers or suggestions would greatly appreciated.

Thanks!