Hi Pat,
TGV "Pro" (business in French) tickets have multiple benefits for people who often change their travel plans last minute.
TGV Pro tickets are exchangeable, without fees, up until your scheduled train departs. After that, you can still exchange your TGV ticket for another train, but you will receive only 50% of the face value of the unused ticket when exchanging it for another (unless it happens to be the next train on the same train route, up until one hour after your originally scheduled departure).
So, yes, this ticket will help you save money if you miss your scheduled train.
I created an article on
TGV Pro Ticket sale conditions which will explain the exchange and refund policy in more detail.
You can also call the SNCF ticket office (asking for an English speaking representative if need be) and exchange your tickets over the phone before your scheduled train departs, so that you don't lose 50% of the ticket value. This telephone number will be provided on your ticket purchase receipt or by email if you purchase your TGV ticket online.
Best regards,
Ben