Referencing elements in an array with variables is not difficult:
Array.At(column, row, sheet)
So you'll need three variables - column, row and sheet.
Say, if column=1, row=4 and sheet=0, it will return "this is the box for the choicebox" line from your array. Add 1 to row variable and it will return the next line below it.
I still don't quite understand your idea, but if the plot of the game is linear and dialogues are played one by one, it may work.