I would do this with a table rather than text boxes.

If you created a three row, one column table with no visible borders you could then make the second row very tall and have the first and last rows at the same height as each other. Cell 2 you give center alignment, Cell 3 you bottom align. Cell 1 remains empty and is only there to ensure the content of cell 2 is balanced vertically on the page.

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia