'Process changes in the merge_source_field combo box'

def merge_source_field_changed(self, new_index):

    new_source = self.merge_source_field.currentText()
    self.merge_source_field_name = new_source
    if (new_source > ''):
        merge_source_spec = self.merge_source_fields[unicode(new_source)]
        self.merge_source_field_name = merge_source_spec['field']
        if ((not self.merge_before.isChecked()) and (not self.merge_after.isChecked())):
            self.merge_after.setChecked(True)
        self.merge_before.setEnabled(True)
        self.merge_after.setEnabled(True)
        self.include_hr.setEnabled(True)
    else:
        self.merge_before.setEnabled(False)
        self.merge_after.setEnabled(False)
        self.include_hr.setEnabled(False)
