ffrriittzz

Help! I'm not completely sure what I've done but I'm trying to insert track marks into a particularly long recording and my MD (Sony MZ-NH900) is not allowing me. I think what has happened is that I have inadvertently had the recording sent to the PC and then back again. Now I can't put the one or two track marks in that I so badly need. Is there any way around this? Many thanks for any potential help out there. FFrriittzz.