sales:Help with a formula

I am running a sales spreadsheet that requires sales entered each day. I use a simple formula to run a continuous total starting at Monday and ending Sunday (1st cell for sales input is B4, second D4, third F4 and so on. 1st Cell for accumulated sales is C4, second E4 and third G4 and so on.
I use B4+D4 to caluculate the running total in E4 or example,and to eliminate that total appearing in G4 where the next formula is B4+D4+F4 I precede that with an IF formula IF(E4=0,'', ). This way I only show the current Week to date totals, not the upcoming days in the rest of the week. My problem lies in Holidays. If for instance D4, the Tuesday was a holiday and I enter either "holiday" or just leave it blank, the rest of the weeks formula will not work. I get a Value message. How can I achieve my goal of getting a daily week to date total without having it show in the upcoming days AND have a holiday in there too??? Any suggestions would be appreciated. Thank you John