I have managed to get it all sorted out. Apparently when Roar Kristensen (the programmer for OC4BA) wrote the programme for the EFIS and MCP (from Open Cockpits) he included a way to activate both the CTR and the TFC buttons. He set it up to press twice on the DATA button to activate TFC and twice on the WPT button to activate CTR.
It wasn't something that was published anywhere for someone like me to learn about it, but now I know, if anyone else has this problem, then this is the answer.
Thank you for taking the time and trouble with me. It is very much appreciated