Is it possible to make a validation in a question matrix texts (multiple fields per line) that forces the user to fill in the fields in the first row?

sorry, I don 't know why the question is now under installation update issues, tried to put it into some different category

Why didn't you answer the questions at the beginning?

How did you code the y-axis and the x-axis?
If you use something like "Y01", "Y02",... for the y-axis and "X01", "X02",... for the x-axis you only have to count the filled fields, like
count(self.sq_Y01)==[number of columns]

Great, thank you that helped.

Frage-Validierungsgleichung: count(Notebook1_Y001_X001, Notebook1_Y001_X002, Notebook1_Y001_X003) == 3

Frage Validierungshinweis: if(count(Notebook1_Y001_X001, Notebook1_Y001_X002, Notebook1_Y001_X003) < 3 != 3, "Bitte, füllen Sie die erste Zeile aus!", "")

Eben, but it's shorter with ".self".

And where are the curly brackets around your validation tip?

And this seems to be really strange "< 3 != 3"

Joffm

sorry, you are right.
I copied from logic check and there was an error as well.

count(self.sq_Y001)=

and for the tip
{if(count(self.sq_Y001)!,"Bitte, füllen Sie mindestens die erste Zeile aus!<br/>","")}