Forms :: Binding Selected Data From One Datablock To Another

I've got a problem with binding my selected data from one data block to another. When I'd finished selecting my data(subjects in this case),

and I clicked schedule button, my selected data were not bound into the textboxes in schedule datablock.this what happened.the code i used in when-checkbox-changed trigger:

BEGIN
IF :NEWSTUDENTS.cb_subj = 'N' THEN
Clear_record;
ELSIF :NEWSTUDENTS.cb_subj = 'Y' THEN
:SCHEDULE2.Subject := :newstudents.subject_code;
END IF;
END;

and in tree-node-activated trigger:

MEssage('FOR LOOP - subj_code = ' || subj_rec.subject_code);
:NEWSTUDENTS.subject_code := label_of_mynode;
:NEWSTUDENTS.subject_= subj_rec.subject_code;
:NEWSTUDENTS.units:= subj_rec.units;
MESSAGE('POSITION OF CURSOR ' || :SYSTEM.CURSOR_RECORD);
[code]....