I had a similar problem. I cured it by making the filename the
complete filepath , alternatively you could make an assign (before you run) to the directory the files are in and use the assign in the filename, i.e - dc.b "myassign:myfile",0.
As an aside I tried to make calls to DOS Lock(), CurrentDir() & UnLock() thinking that this might do it, however I couldn't get the program to run at all!
(I still think that the DOS calls are the answer (probably I'm completely wrong) but I'm buggered if I know how to do it!