Editing External data-group file through tmsh script

Hi, our F5 having large external data-group file which needs to be modified frequently.I need to make the tmsh script which invoke the external data group file and append or modify the new line and saving. can you please share the script for this Now we are manually doing the modification by following methods (Active)(/Common)(tmos)edit /sys file data-group "filename" it will open the file in edit mode ,then we do edit and save.