Percussion staff labels

It is very important that my percussion staves are labeled as “Percussion I” and “Percussion II”, NOT by the instruments they are using at the time. How can I change the staff labels for the percussion parts? I want the instrument to only appear above the music, not as a staff label in the score.

Thanks!

If you use 5-line-condensed notation, that should be rather easy to achieve. You are probably using 1-line notation or grid?