Is there a way to focus on one line of text?

I know I should try it myself, but I just can't figure it out! Is there a way to focus on one line of text in a script? like say I was going to make a grammar checker on this area of text:

hi!
my name is unknown and i am not known

And it's gonna find grammar issues on line 1 & 2 like this: if letter 1 on a sentence isn't capital, make it capital

edit: or if it finds certain text it'd remove the entire line

-- Thank you for the help.