I use Noteflight for music notation but tried out MuseScore, and could not get it working with my digital piano, I could only input one note, then it wouldn't recognize any more.

From limited experience, notation programs require you to enter exact note duration without the ability to go back and make changes. (ie if you change a 1/2 note to a 1/4 note, you will be left with an extra 1/4 rest with no way of removing it.)

I wonder if there is a music notation woftware which allows you to just enter all the notes first, then you can go back and edit the duration- then it will calculate the measures for you.