Sales by Salesperson by Month

Hey everyone,

There is probably a straightforward solution but as a newbie, I'm just not seeing it right now. I'm looking to show the sales by salesperson by month for the trailing 12 months. Here is the formula I've created:

=-@NL("Sum","G/L Entry","Amount","Document Type","Invoice|Credit Memo","G/L Account No.","510000..519999","Posting Date","8/1/2021..8/31/2021","Link=","Cust. Ledger Entry","Document No.","=Document No.","Salesperson Code","ACA")

I'm struggling to use the Link feature to match the two tables by the Document number (is there a better option?) in order to get an accurate number. Any suggestions? 

I've replaced the date and salesperson codes with formulas to cell references but I am showing them here to avoid any confusion. 

Help! 

Thanks in advance,

Ryan