To make the handling of errors easier I have used the principal of 
INDIRECTION VECTORS (See Documentation and article)

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REM NEAR TOP OF FILE INCLUDE THE FOLLOWING
 DIM cvI 4:cvSdim=40:DIM cvS cvSdim
REM THIS PROVIDES "COMMON" VARIABLES FOR ONE INTERGER
REM AND ONE STRING OF 40 CHARACTERS

-----PROColdopen-----------

REM ONERROR:index=INKEY(0):PROCbadfile(cvS,winerr,winret) 
REM RETURNS TO HERE ON ERROR
REM PROColdopen("prompt",winprompt,winret,cvI,cvS,cvSdim)
REM ONERROR:index=INKEY(0):PROCgenerror(winerr,winret)
REM oldname$=$cvS:oldchan=!cvI:REM GET VALUES 

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DEFPROColdopen(p$,p,r,i,s,sd)
LOCAL of$
PRINTCHR$(1);"2I";p;
 REPEAT:PRINTCHR$(1);"2C";CHR$(253);p$;:INPUTof$
of$=LEFT$(of$,sd):$s=of$
 p=OPENINof$:!i=p
 IFp=0THENPRINTCHR$(1);"2C";CHR$(253);"FILE "+of$+" NOT FOUND":CLOSE#p
 UNTILp<>0
PRINTCHR$(1);"2I";r;
 ENDPROC

-----PROCoutopen-----------

REM ONERROR:index=INKEY(0):PROCbadfile(cvS,winerr,winret) 
REM RETURNS TO HERE ON ERROR
REM PROCoutopen("prompt",winprompt,winret,cvI,cvS,cvSdim)
REM ONERROR:index=INKEY(0):PROCgenerror(winerr,winret)
REM outname$=$cvS:outchan=!cvI:REM GET VALUES 

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DEFPROCoutopen(p$,p,r,i,s,sd)
LOCAL of$,ex$
PRINTCHR$(1);"2I";p;
 REPEAT:PRINTCHR$(1);"2C";CHR$(253);p$;:INPUTof$
of$=LEFT$(of$,sd):$s=of$:p=OPENINof$
ex$=CHR$(1)+"2C"+CHR$(253)+"FILE EXISTS : CONTINUE Y ? "
 IFp>0PRINTex$;:ex$=CHR$(GETAND&5F):IFex$<>"Y"UNTILFALSE
 CLOSE#p
 p=OPENOUTof$:!i=p:IFp=0PRINTCHR$(1);"2C";CHR$(253);"INVALID FILE NAME"
 UNTILp<>0
PRINTCHR$(1);"2I";r;
ENDPROC

-----PROCnewopen-----------

REM ONERROR:index=INKEY(0):PROCbadfile(cvS,winerr,winret) 
REM RETURNS TO HERE ON ERROR
REM PROCnewopen("prompt",winprompt,winret,cvI,cvS,cvSdim) 
REM ONERROR:index=INKEY(0):PROCgenerror(winerr,winret)
REM newname$=$cvS:newchan=!cvI:REM GET VALUES 

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DEFPROCnewopen(p$,p,r,i,s,sd)
LOCAL nf$,ex$
PRINTCHR$(1);"2I";p;
 REPEAT:PRINTCHR$(1);"2C";CHR$(253);p$;:INPUTnf$
nf$=LEFT$(nf$,sd):$s=nf$:p=OPENINof$
ex$=CHR$(1)+"2C"+CHR$(253)+"FILE EXISTS : PRESS A KEY TO CONTINUE "
 IFp>0PRINTex$;:ex$=GET:UNTILFALSE
 CLOSE#p
 p=OPENOUTef$:!i=p:IFp=0PRINTCHR$(1);"2C";CHR$(253);"INVALID FILE NAME"
 UNTILp<>0
PRINTCHR$(1);"2I";r;
ENDPROC

-----PROCbadname-----------

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 DEFPROCbadfile(n,e,r)
 PRINTCHR$(1);"2I";e;
 IF ERR<>252 PROCgenerror(e,r)
 PRINTCHR$(1);"2C";CHR$(253);$n;" is not a valid filename"
 PRINTCHR$(1);"2C";CHR$(253);"PRESS A KEY TO CONTINUE":e=GET
 PRINTCHR$(1);"2I";r;
 ENDPROC


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 DEFPROCgenerror(e,r)
 CLOSE#0
 IF ERR=17STOP:REM FOR USE WITH Z081 OR Z163 USE IF ERR=17PROCmenuRET
 PRINTCHR$(1);"2I";e;
 CLS:REPORT:PRINT" at line ";ERL
 PRINT"Press a key to restart";
 PRINTCHR$(1);"2I";r;
 e=GET
 CLEAR
 RUN
 ENDPROC

-----PROCmenuRET------------

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 DEFPROCmenuRET
 ON ERROR OFF
 IF HIMEM<>&B000:CHAIN"Z081/MENU.BAS"
 *CLI CALL &B000~E
 END
 ENDPROC

-----PROCbadlink-----------

REM example piece of programme. In this case lines 1 and 4 of the 
REM "control" file contains the link filenames.
REM Note use of line I%=1/I% is not appropriate if link file is for 
REM output, and hence may not exist. In that case a FOR NEXT loop can
REM not be used so the ONERROR OPtN & CLOSE lines will have to repeated

REM FORC%=1TO4STEP3
REM ONERROR:index=INKEY(0):PROCbadlink(control$,link$(L%),E%,R%)
REM I%=OPENINlink$(L%)
REM CLOSE#I%
REM I%=1/I%
REM NEXT
REM ONERROR:index=INKEY(0):PROCgenerror(E%,R%)

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DEFPROCbadlink(c$,l$,e,r)
PRINTCHR$(1);"2I";e;CHR$(1);"2C";CHR$(253);
PRINT";l$;" in ";c$'CHR$(1);"2C";CHR$(253);
IF ERR=252PRINT" is a ";:REPORT:PRINT':ELSEPRINT" Does not exist "
PRINTCHR$(1);"2C";CHR$(253);"Press a key to restart";
CLOSE#0
PRINTCHR$(1);"2I";r;
e=GET
CLEAR
RUN
ENDPROC