We have a custom object in our contacts section that says "Primary contact" and it is a checkbox. Each account with account type customer needs to have at least one primary contact. I do not want to create a step where this is ticked in a flow but I do want it to trigger some sort of validation error or message saying you cannot save a record with account type customer unless you have at least one primary contact. I tried to create a flow but haven´t done this before so not quite sure which parameters I need to add. 

We have a custom object in our contacts section that says "Primary contact" and it is a checkbox. Each account with account type customer needs to have at least one primary contact. I do not want to create a step where this is ticked in a flow but I do want it to trigger some sort of validation error or message saying you cannot save a record with account type customer unless you have at least one primary contact. I tried to create a flow but haven´t done this before so not quite sure which parameters I need to add.