How to put some notes in the bass clef?

I was composing my last song, and I was wondering if I can do this, and i have an idea but i rlly dont understand it (for 2 staff instrument):
1. User must select at least one note of an instrument to be split.
2. The selected instrument will be duplicated (below the original one).
3. The second staff of the first instrument and the first staff of the second instrument will be deleted.

Is there any thing i can do this?
Thanks for your help :3