Simple bulk batch editing in admin backend

I have users submit their forms. There are about 200. I need to sort these forms into groups, eg Group A, Group B, etc. up to about 8 groups.

Is there any way I can add multiple entried into groups at the same time. Eg, if I want the first 30 entries (based on some sort result such as date of entry) to be added to “Group A”, is there a way I can do this, via either admin backend, or via custom script that can be called?

Ben