Visible Field; Invisible if Blank

[Delnang]

I have a section "App_Grp" with a field called "App". I would like this to
happen...When the form is first opened App Grp is visible. If info is typed
in App then the section and field is visible. If App is blank, the group and
field is no longer visible, but later someone could reinsert the section to
put in an app name.

Can someone help me with this logic?

Thanks
Angie