These seem to satisfy your requirement
=IF(AND(ISBLANK(A2),ISBLANK(A3)),"",A2+A3)
=IF(AND(ISBLANK(A2),ISBLANK(A3)),"",SUM(A2:A3))

Note
(a) SUM(A2:A3) is overkill for A2+A3 unless you need to get a numeric
result even when one cell has text
(b) A cell with a formula such as =IF(MONTH(TODAY()) =3, "", MONTH(TODAY()))
which displays a blank in March will still fail the ISBLANK test because a
cell with a formula is not blank even when it displays a blank (clear?)

best wishes
--
Bernard V Liengme
www.stfx.ca/people/bliengme
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wrote in message
...

What I need is: IF (A2 AND A3= Blank ) THEN return blank, ELSE SUM
(A2:A3)
[even if the value(s) entered into A2 and/or A3 is/are 0 or any
combination
of zeros and blanks, I need it to return a 0.]