Exclude item from Total

I am having trouble with a subtotal. I have a formula that adds two fields together to give me an invoice total. However there is an item that I would like to exclude from being calculated into my total.

I have no idea how i could tell the formula to not include the item. I was thinking an IF THEN formula would work.

if <> "0001" then +

but that didn't do anything. Is there a way to do this?

Thanks!