Rollup Field Result depending on Account Type

Dear Community,

I would like to calculate the MAX() of a integer field on a custom entity but filterd by type. I have an entity that stores additional Information such as sales volume  & the type of account (info from the legacy system). This entity has a 1to1 relationship with the account entity.

On the account form, I'd like to display the MAX(SalesVolume) of all accounts having the same type as the selected account. Does anyone have an idea how to do this?

Thank you

Best Regards

NMI