Can I just check my understanding...
The 'Delta' field, is this the number of employees in total at that point in time, or is this just the new ones? (i.e. to know how many employees thee are at any particular point we need to use a running sum?)
The 'Term' field is the number of terminations for that month?
If you can let me know I the above to question, I'll see if I can find a solution.