Hi,
I assume that if one of the values in a, b,c,d are "", to enter "" otherwise
to perform your calculation

=IF(OR(A2="",B2="",C2="",D2=""),"",1/A2+1/B2+1/C2+1/D2)

If this help please say yes, thanks

"Re." wrote:

I'm in the process of writing an excel sheet to do a series of calculations
and lookups etc. and have got to the final calculation and cant make the step
work!

I need to calculate the reciprocal of 6 numbers. i.e 1/a = 1/b+1/c+1/d etc.
fairly standard, but i dont always have a value and i want to make excel
ignore the step if there is no value in a particular cell (these are linked
from previous sheets and currently have =if(cellx = "yes", celly,"")).
However, when the "" is used for 1/b+1/c etc. i get a #value error.

Any ideas on ways around this would be greatly appreciated.