It will certainly be possible but you would need to break the last line manually first as you couldn't have 2 alignments in the same paragraph. Personally as I use paragraph styles I would create a second style with the left alignment. Depending on how many instances you have I am sure a script could apply that style automatically but if the document is short then it shouldn't take too long, the bigger issue would be having to manually break the text with a paragraph return, and potentially keep changing this as text is edited etc.