Try this which takes alternative columns: columns with "-" are treated as
zero (as per your IF statement).

=SUMPRODUCT(--(MOD(COLUMN($O$3:$AC$3),2)=1),($O$3:$AC$3),--(MOD(COLUMN(P5:AD5),2)=0),(P5:AD5))*0.01

If cells Q5,S5 etc are blank or zero, the first formula would work.

In your original posting your cells were in row 5, but your second said row
6, with answer in AE5: very confusing!

Why did you say the first one didn't work?

"Tanya" wrote:

Hi, I hope someone may be able to help me.

I have the following formula which works fine, however the values in P5, R5,
T5, V5, X5, Z5, AB5 AND AD5 may contain text which is messing up my formula.
My reasoning behind needing to do this is calculating student marks over
several tasks, with different % weights and until the assessment task has
been set I have an IF formula based on the false being "-".

I have tried the =IF(ISNUMBER(P5),(P5*$O$3),0,IF(ISNUMBER(R5),(R5*$ Q$3),0,....
and getting all kinds of error messages, in cluding too many augments.

=((P5*$O$3)+(R5*$Q$3)+(T5*$S$3)+(V5*$U$3)+(X5*$W$3 )+(Z5*$Y$3)+(AB5*$AA$3)+(AD5*$AC$3))*0.01

I would appreciate any assistance here.

Thanks
Tanya