CVFF forcefield in Discover

Hi.
I'm a user of Discover module in Materials Studio.

I found that in cvff.frc file, there were 4 types (cvff_nocross_nomorse, cvff, cvff_nocross, cvff_nomorse), however, when I applied this cvff forcefield into my structure file, I couldn't choose the type that I want to use.

If I want to use harmonic bond-stretch term rather than Morse bond-stretch term(maybe, it is default type for cvff's bond stretch), how can I achieve to do this?