Is that job description part of a phrase (as in a "fill the blank" text?
If the variable length of the job description can be handled on design/layout level, it would definitely be easier to accomplish.
If it is part of a phrase, it depends on the lenght of the phrase; it may actually end up in a way that by recreating the text of the paragraph (in a multiline field), there would be no need for additional lines (in other words, that the last line can cope with the run-length difference of the various job descriptions. Anyway, in this case, you have non-printing fields where the user enters or selects the job description, and you assemble the text and write it to the "actual" field (which may be read-only).
Hope this can help.