How to create list from list via inputted string with code block

i’m pulling current revision parameter from sheets so that i can pull a given revision number and perform an operation to all sheets that have that parameter…
i’m trying to do the following…
given list
create a list with code block for “12” that returns all the “12” values and their indexes so that i can perform a function to these items. Nothing i searched for so far can do this and a lot of list info is missing when i google it! Thanks for any help.

@davidr58 Please post some screenshots of your dyn


This is a way to do what you describe :


Thanks for the help