Excell format re if cell is blanc the total should be blanc too else add

11/08/2014
G’day gang, I am trying to make a spreadsheet for my boat costing and having problem with it.
I can sense the solution but hit my head every time. I was a computer programmer back in the 80’s (Cobal and Assembler languages), IF THEN ELSE was so simple. Thanks to anyone that can help.
Graham