Notes/Domino 6 and 7 Forum : The @DocChildren mess... Lotus... WHY?

Sometimes there are those things where the choices of Lotus to me are one big mystery and this is one of those:
@DocChildren only works in a column or Title Formula nowwhere else... Why?
I needed this function to make an @If statements that prevents more than 1 response being made to a document. There are however no other @formula's available for use in a formula to check the number of responses. So I created a view with @DocChildren in it and use a @DBLookup to get the value from the view. However @DBLookup skips columns with only @DocChildren (and the other alternatives) in it. WHY?
So I gave the row a value where I use a Field in my document like @DocChildren+UserNA. I create a field on my form where I do a @DBLookup for this value and get to see nicely: 1Martijn. So I finally found a number I can work with in a formula? NO! In the document properties I find that even though Notes shows the correct number, it saves: C0 Martijn. And that's independent of the amount of responses. How did you guys do that, but more importantly: WHY?