Hello Martin,

You can have expected behaviour if you implement something like this:

$ACTION

Case ACTION
   When "VERIF_CRE" : Gosub VERIF_CRE
   When "AVANT_CHOI" : Gosub AVANT_CHOI
Endcase

Return
########################
$VERIF_CRE

# Call standard since standard can also put OK=0
If dim(PROGSUB)>0 and PROGSUB<>"" and GPE<>1
    Gosub ACTION From =PROGSUB : GPE=1 
Endif

# Standard* code may put OK=0. Do bot bother executing rest if that happens
If OK
  Gosub SPE_VERIF_CRE
Endif

# OK=0? Then create variable just to simulate cancel button in next $AVANT_CHOI called by "supervisor"
If OK=0
    Local Tinyint YSIMULATE_CANCEL
Endif

Return
########################
$AVANT_CHOI
    If dim([L]YSIMULATE_CANCEL)>0 : # Variable exists, then simulate cancel button
        Kill [L]YSIMULATE_CANCEL
        REPONSE=GSTAFIN : # Cancel button
        Gosub ABANDON From GOBJSUB
        Gosub SETBOUT From GOBJSUB
        
        Raz REPONSE
    Endif
Return

Many thanks Roberto.  REPONSE=GSTAFIN : Gosub ABANDON From GOBJSUB was exactly what I needed!