Dynamic mark first, value change second. If no change from the default value then auto key will not be generated.
When following what you did : 1 st frame no change (ie -100), dynamic mark, last frame – dynamic, value change – no animation is expected.
Do this instead: make your key, make your correction, then go to first frame and do dynamic mark, then go to last frame do dynamic mark then do 100 on qualifier blur.
Interestingly enough as far as dynamics are concerned qualifier blur is a part of a color corrector subset in the key frames tab and not a part of the qualifier subset.
Also if you are to make a qualifier selection after you made a dynamic mark you have to repeat the same selection at all of the other marks. Otherwise the selection becomes void at those marks and the qualifier blur will have no effect as there is no selection. So make your selection first, then start doing dynamics.
Hope this helps.