Excel 2003 :: Calculate Formula For Third Value Of Week?

On a excel sheet I've got columns, each column represents a weeknumber. I want to calculate the so-called 4 wk average for each row and for each week and this is the formula I use:

(value*Tvalue)+(value*Tvalue)+(value*Tvalue)+(value*Tvalue)/(Tvalue)

(this is not the actual formula but simplified, that's not really important).

It's the checks that make things a bit more complex. If a value of a weeknr is zero, skip it, but if the next value is also zero, just skip the formula alltogether and make it a zero (or text like "false"). So another thing that has to be accounted for is that if a value is zero, the next weeks value is taken instead.Example (see included file):

I want to calculate the formula (mov 4wk avg) for the third value for week 12, which will make the formula

(0.2*6)+(0.3*6) now there's a zero on week 14 so I skip it, then formula will be:
(0.2*6)+(0.3*6)+(0.6*6)+(0.9*6)/(6).

Right now I'm doing this in VBA with a lot of variables and a lot of if statements.Is there an easier more effective

I know the example sheet is a 2007/2010 version but I need to accomplish this for 2003.