Making TextLength ignore some notes.

[David Sumbler]

\version "2.19.81"

<<
  \new Dynamics {
  s2 s2^\markup \column {"I would very much" "like this to take" "up
precisely a" "minim's width."} | s1*2 | }
  \new Staff {
    b'2~ b'4\fermata a'4 \fermata | g'1~ | g'1 | }
>>

In the above example, I would like the words to occupy the horizontal
space between the 3rd beat of the first bar and the following barline.
In other words, the barline (and, hopefully) the final crotchet of the
first bar need to be moved suitable distances to the right.

\textLengthOn would be fine if the music underneath the text consisted
of only a minim, but of course it moves the crotchet on the 4th beat
past the end of the right-hand end of the text.

Is there any way of getting the effect I want, with the barline placed
after the text and the 4th-beat note placed evenly between the 3rd-beat 
note and the barline?

David