Copying field value from a subitem to an item

I created a board to track resource time off against each client. I display the content in a calendar view.

How can I control how the information is displayed in the calendar view? The current format displayed is “text_column_value | Client_name”. I’d like to change this to be “Client_name | Sub_Item_Owner”.

Slight correction. The Calendar view currently displays “Subitem_Name | Client_name”