Split output of textbox into several lines -Smartforms

Hi

i have a textbox that is in a window that is 20 cm wide.I would like to have my output written only on the first half of the textbox ,so only on the first 10 cm and the rest should be written on the next row.How can i say "jump to the next row"?

ex:

abcdefghijkl to become abcde

fghijkl

thanks