how to ignore specific errorcode and let program proceed in PLSQL

Hi ,

In prodedure,there are 3 half commits.

1--half commit  success

2--half commit  failed,    exception handle, but  if  the error code is ORA-01722, ignore and continue to do 3-half commit; else if error code is not ORA-01722,stop program at this stage,don't do 3-half commit.

3--half commit  success

I know we can use sub- exception(only handle for step2) to let the program proceed when SQLerror hanppend in step2, but not sure how  to stop program when the errorcode is not ORA-01722 ?

begin

..........

begin

.........

exception          ------exception handle for step2

when others then

end;

...............

end;

exception           -----main exception handle

when others  then