crosstab null x zeroes

Incredible how difficult is to find out a solution to differentiate ZEROES and NULLS!

I saw something like this:

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Hi Leo,

Right-click one of the cells in the Summary fields > Select Format field > Common tab > Click on the formula button beside 'Display String' and use this code:

if currentfieldvalue = 0 then "N/A"

else

totext(currentfieldvalue)

-Abhilash

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But I can´t say 0 is the same as null !!!

Some record sets return values to populate a crosstable that
a) Sometimes they are regular numbers ---ok!

b) Sometimes they are 0 (read from database) and

c) Sometimes there is no data for that place!

How would we differntiate (b) and (c), since I must show 0 (zero) because it is a regular value from my database.

And I don´t want missed values to be shown as "0" too (because they are NOT zero, they simply inexist!)

Any Idea?