Actually, I would use:

v_keypart1indic := DECODE ( :new.keypart1_use, NULL, 0, 1);

Actually, however, if you look at my suggestions to your original post, you will see that you should really fill these in the EXCEPTION block:

...
v_keypart1indic := 1;
...
EXCEPTION
---WHEN NO_DATA_FOUND THEN
------v_keypart1indic := 0;
...


HTH,

- Chris