Ability to specify individual fees to invoice

We need to use CourtReserve to invoice various schools / orgs ("Members") for different events and Court Times. The way those orgs operate is that they need a specific invoice sent for a single fee. Right now, I don't have a good way to filter for just one fee to invoice - filtering by GL Code or Thru date doesn't work, our GL Codes are set in stone for us and we are not able to change them. 

So we need to be able to hand pick specific fees on an invoice that might share the same GL code, but go out as two separate invoices WITHOUT one voiding the other and combining them together.