method to slow down VERY quickly

[hermanding]

i am using the 2007 demo to evaluate it, and have one measure in 4/4 that has a run of 42 notes - good for us piano players who practiced our Czerny.
the metronome marking at the beginning of the bar has been 120 to the quarter note- so those fingers are moving along. in the second half of the run, i want to ritard it greatly - since it leads directly into a nice, sweet little melody. Up to now, putting the ritard on the first note of the slowing seems to have no effect - as if it doesn't have time to react before the measure is over and done. next, i went to tempo tool - but its options of selecting number of quarter beats per minute seem to be for the entire measure - not just a portion of it. next, i tried to change by a per cent - but that seems to go even faster. finally, i split the 4 beats into 2/4 to contain 2 (those without ritard), then a 1/4 bar to start the slowing with a ritard added at the beginning - and a final 1/4 bar with a metronome marking on the tool much slower around 50 quarters per minute. and that is not a gradual decline in speed. anyone have any ideas? they are all very apreciated.

[hermanding]

i seem to have stumbled onto a solución when the ritard expression does not seem to have time to work due to fast speed and only a beat or two to do it. i used the expression box to create expressions for various beats per minute - 100, 80, 60, 40, 30, 20, 10 and placed them about every third 32nd note in the last 2 counts of the 4/4 bar - and it worked.
i see the ritard work well when there is more time.
i still am happy to hear other suggestions - and if anyone is experiencing this problem, i will be more than happy to explain it step by step.