In the tokenat expression you would change array.at(0,2) to use a variable instead o the 2 so array.at(0,var). Then using a similar condition you have for = 'back', you have = 'next' and then change that new variable, maybe add 2 to it so it skips from 2 to 4. You also need to set chatposition back to 0.
That would be for column skipping. If you want to change row then you need a variable for the X so array.at(var,2) and then change that variable to signal the row.