DRanck
Try using the events editor in the command bar. I think that will work.
This is the best answer by far
Make your selection and type the desired length in the box
Note: if your target length is say, 120 ricks and the
first note in your selection is already this length then it will not work. 2 ways to over come this, either re-select the range ensuring the first note needs correcting, or (especially if it's a complex range of non-contiguous notes), using the example above, first type 121 and enter, then hit 120 and enter.