We have added an "On Behalf Of" field (lookup field to Accounts) to the Sales order for Agencies or Head offices that are booking on behalf of one of their clients or child companies. However, we're using canvas to only show the related records on the account card if an "indirect booking" check box (using it as a flag) has been checked.

Using Workflow rules, how would I go about updating the "On behalf of" account to set the "indirect booking" flag?