Hi, I just downloaded and installed OPEN-EMR, I was looking for a EMR for my wife who runs a Psychological clinic and is burried on paper. Very impressed on all the features it has, but the wife wanted to give access to patients to check their appointments on the portal, not giving them the possibility to schedule their own appointments… 
So to begin with just added a config file and modified code on the portal, but ended up doing the full change to make that a setting that can be handled on global settings.
so first I added a record on globals table:
insert into globals (gl_name,gl_index,gl_value) values (‘allow_patient_create_appointments’,0,1)
then changed globals.inc.php (under library folder) to recognize the new parameter. Sorry can’t upload files because I’m a new user I’ll update this post later with the files.
and finally changed home.php under portal to read the new global parameter.
now with this changes you can go to Administration -> Globals -> Portal, and find a new option to Allow patient to Schedule Appointments, and in patient portal it that option is set off there will be no ‘Schedule New Appointment’ button
Hope it helps someone, if you need the code before I can upload files, you can send me a PM and I’ll send it to you.
Regards
Osvaldo