OK, my head's spinning with this one. I'm trying to suppress both errors and
0 values from being returned. In either case, I want an empty string to be
returned.

Here are the conditions:

IF

1) DeprnByProjectByMonth!I4 is text OR
2) COFByProjByMonthI4 is text OR
3) 1-TimeExpByProjByMonth is text OR
4) DeprnByProjectByMonth!I4 is blank AND
5) COFByProjByMonthI4 is blank AND
6) 1-TimeExpByProjByMonth is blank

THEN, "" [the empty string]

ELSE,
SUM(DeprnByProjectByMonth!I4,1-TimeExpByProjByMonth!I4,COFByProjByMonth!I4)

Here's what I have:
=IF(OR(ISTEXT(DeprnByProjByMonth!I4),ISTEXT(COFByP rojByMonth!I4),ISTEXT('1-TimeExpByProjByMonth'!I4),AND(ISBLANK(DeprnByProjB yMonth!I4),ISBLANK('1-TimeExpByProjByMonth'!I4),ISBLANK(COFByProjByMonth !I4)),"",SUM(DeprnByProjByMonth!I4,'1-TimeExpByProjByMonth'!I4,COFByProjByMonth!I4)))
--
Brevity is the soul of wit.