on error =NephiRtn( Error(), ;
Message(), ;
Message(1), ;
Program(-1), ;
Lineno() )
.
.
.
Function NephiRtn

lParameters ;
lnError, ;
lcMessage, ;
lcMessage1, ;
lcProgram, ;
lnLineno

set console off
=messageBox( "Error # " + alltrim( str( lnError ) ) + ;
" " + lcMessage + chr(13) + ;
lcMessage1 + chr(13) + ;
"Line # " + alltrim( str( lnLineno ) ) + " in " + ;
lcProgram )

return && leave NephiRtn

In the development environment, if your project is compiled with line numbers, you should be able to locate the program, the line of code making the reference and from there determine the file being referenced.