Problem:

Get 173 error when calling 16-bit DLLs from a 32-bit EXE

Resolution:

Release: 3.1    Get RTS error: 173 Called program file not found in drive/directory

It is not possible to call 16-bit COBOL DLLs from a 32-bit EXE.

You will need to recompile all in 16-bit or all in 32-bit.