Make field required in edit mode

[dgoodridge]

What formula would I use to make a field required only in edit mode?

I've tried

=isNullOrEmpty(Volunteer)and(Is Edit Mode)

=Is Edit Modeand(isNullOrEmpty(Volunteer))

[dgoodridge · Accepted solution]

I posted too soon.

I got it to work with =Is Edit Mode​ && isNullOrEmpty({Self})