Syntax for dealing with null values in enablement condition calculation

How can do an addition integer fields that are not enabled (null) in an enablement condition for validation purposes?

In my listing record we capture the household population along with the sex of members along with ages below 15 and over 15.

For example in a household of 4 person we have the following breakdown in my fields are:

hospop - household population = 4
ovr15m - male age > 15 = 1
ovr15m - female age > 15 = 2
ind15m - male age < 1 = 1
und15f - female < 15 is not enabled

In my static text enablement would read

!(hospop - (ovr15m + ovr15f + und15m + und15f)==0)

however because und15f is null the text always shows

How should I write this syntax ?

Dear Neville,

you can write new[]{var1,var2,…, varN}.Sum() to obtain a sum of numeric questions disregarding the unanswered ones.

Best, Sergiy

Thanks, syntax works.

Regards

Neville

Thanks, syntax works.

Regards

Neville