Create a custom report showing NET profit

Please could you help me to create a custom report showing total sales less purchases and overheads

Something like this should work:

This takes the total of all sales codes (4000 to 4999) then deducts all the expenses (5000 to 9997). Ok the forumal shows to sum up the two ranges but the expenses will be negative so the net effect is a deduction from sales.

Many thanks Glenn, will give this a try