Passing multiple arguments in an Infomaker dropdown

I am building a custom constituent screen into which it is possible for the user to enter data that updates a local table.

Some of the values will be selected from dropdowns that are filtered by data in other fields (mainly customer_no). Using the Tag field I am able to display an array based on one argument

{tr_donation_level_description, program_no}

but what is the syntax if I want to pass two arguments - i.e.

{tr_fund_desc, customer_no & campaign_no}?

David