Combo checking in online billing

Hi

I'm trying to be sure I understand what the billing is doing.  Here's what I see

Enter an invoice online

Enter Project costing chartfields at the header level

Enter project costing chartfields at the line level

Enter coding on the Rev Distribution line.

In our environment, if I use a asset or liablitiy account number I must not have Project costing chart fields so I leave them blank on the distribution line and when I save it runs combo checking and all is good.

Now when BIPRELD runs, since the project chartfields are blank, a values will default into the line from either the line or header level and then combo checking will run again and it will fail