I want to calculate a value based on several cells in say row 4. However, I
do not want to include values in any columns that do not also have a
non-missing value in, say, row3. Thus my calculated cell in, say column A,
should have some syntax like:

IF A3 < MISSING THEN
< do calculation of value

I hope this is clear.

What is the proper syntax for the pseudocode that I have above?

Thanks!