You could edit the RTM to add that field to the SA-M report which can provide the same information.  SA-M and SA-N replace SA-B,C,D,E,G,H,I,J,L,M text reports which are not editable.  SA-M & N have all the same sort options as the other reports and filter selections can be saved and run repeatedly for different date ranges.

Also, I don't know what company you are with but adding fields to RTMs requires that you be using Evo-ERP and not DBA Classic.  The DBA Classic RTM editor does not support adding data fields to forms or reports but the Evo-ERP one does.