No problem, good to hear that should save you quite a bit of money!
I just put in Chesterfield to Stafford into TrainsCanBeCheaper.info and selected 'cheapest' (which is not guaranteed, and often cheapest isn't suitable) and it lists the tickets. In this case it suggests a simple "split" at Blythe Bridge.
If you want to see an itinerary for the through journey, go to a website such as East Coast, London Midland, Southern (for example) and choose the 'timetables only' option, and after entering the journey details, select calling at: Blythe Bridge. There are suitable itineraries departing 0906 and 1802.
To book the tickets, you either ask at a ticket office for Chesterfield to Blythe Bridge and Blythe Bridge to Stafford tickets. Or, if you prefer to book online, you need to do two separate searches, though you can get all the tickets in your basket to pay in one transaction if you wish. Don't forget to ensure that the correct number of passengers & the correct Railcard type is selected each time.