If I understand you correctly, Block A will have one PE group and Block C will have two different ones, but you want them both taught by the same teacher. If this is the case then you can simply leave the second block C class unstaffed while you are writing the timetable (you know that the teacher who will lead the class will be free because they are already be in that block). Once you have completed the timetable you can assign the teacher to both classes. This may generate a clash on that teacher's timetable but by that stage it won't matter.
