Need help in creating a variable

i have to create a hidden variable as my client wants. which means i need to create the xlsform should create a variable automatically.
logic. before i create this variable we ask the respondents the first brand that comes to their mind. then a multiple choices question of the other brands that come to their mind. then we read all the remaining brands and ask them if they know them. now i need to create a hidden variable because i will use it later on as a condition. for example later on i should ask questions only for banks which are part of the fam_aware variable. does anyone know how can i solve this request by the client? if you need more information please ask.

PURPOSE:Holds brands AWARE to be used at subsequent questions.

If you want to refer to an an answer from a previous question you can use the question name to use the answer as a variable. See:

Here is an example of one list of options, that is filtered for a second question based on what was selected in the first.
filter-example.xlsx (12.8 KB)

Here is an example of a repeat group that repeats for each answer from a select_multiple.
repeat-loop.xlsx (16.8 KB)

Also, I noticed you tagged your post with odk-aggregate. If you are using Aggregate, please note that it has reached end-of-life and is no longer being updated or supported. Consider switching to Central because it's actively developed.

its more complicated thatn that.
we ask three questions with a list of brands
question_1 (here we ask for the first brand that comes to the respondents mind without reading him the brand list)
question_2 (here we ask for other brands(excluding the one he responded at question_1) again where we dont read to him the brand list)
question_3 (here we ask for all the brands the respondent knows(excluding those at question_1,question_2 and question_3) and reading the brand list)

now i need a variable or maybe another solution so i can save all this answers from this questions in one variable called fam_aware maybe. you may think why do i need this. well i will have to ask 15 questions to all the brands answered at questions 1,2,3.
for example i will have to ask the question how much do you like this "brand"?(i need this question for all the brands answered before)