Abstract
If you need to merge two columns with data justified into one column, you can use a simple worksheet formula and a monospaced font like Consolas, Courier New, or Lucida Sans Typewriter:

Download
Please read my Disclaimer.
left_align_and_right_align_in_one_column.xslx [12 KB Excel file, open and use at your own risk]
Note: A comprehensive documentation of my Excel implementations can be found in Excel VBA A Collection.