You might need to specify the myproject.dcp and the main C file on the command line. As I recall, the support for multiple C files in a project wasn't as robust as using a single C file and multiple libraries via #use.
Note that the correct way to specify the project file is to use the '-pf' command-line option: `dccl_cmp -pf myproject.dcp main.c`.
Can you provide your exact command line and the exact error you're seeing?