Boy you make it sound harder than it actually is....
Post each session as it's own G code file
- then use the Cimco editor to delete the 1st M02/M30
- then append the 2nd file at the end of the 1st file
- then Save As to give it an individual name.......don't overwrite your posted files...you may need to alter something & repost...thus losing everything
There are many controls that could use a schedule program to run a sequence of NC programs ( each file being run a varying number of times before stepping to the next program )