#Value! iserror not working

Background: Spreadsheet cell V2 = Jul12, W2 = Aug12, X2 = Sep12,Y2 = Q1FY12 (this goes on for 4 qtrs.) and then column AL2 = FY12 YTD

Column V230 states =if((sum(E229)=0,"",E229) (this cell is a prior year number that needs to be subtracted from current year number)
V231 states =if(iserror(v229-v230),"",V229-V230)

which works great. Gives what I need.

Column Y230 states =if(countblank(V230:X230)=3,"",SUM(V230,W230,X230)) - which again works great

but Y231 which states =if(iserror(Sum(V231:X231)),"",Y229-Y230) is not working - I get a #Value! return.. so obviously there is something wrong with this formula. I need help.

E229=1045 (current fiscal)
E230=1009
E231=36
--end of fiscal--
V229= (do not have current fiscal)
V230=1045 (prior fiscal)
Y229= (do not have current fiscal)
Y230= #Value!

Thank you for your help. I have made the changes recommended, however, it is still not giving me an output.

E229 =1045
E230 =1009
E231 =36 [=IF((E229-E230)=0,"",E229-E230)]
F229 -F231 =no value yet
G229 -G231 =no value yet
H229 =1045[=IF(COUNTBLANK(E229:G229)=3,"",SUM(E229:G229))]
H230 =1009 [=IF(COUNTBLANK(E230:G230)=3,"",SUM(E230:G230))]
H231 =36 [=IF(ISERROR(H229-H230),"",H229-H230)]
I229 - T231 =no value yet - but error checks are all the same as above
U229 =1045 [=IF(COUNTBLANK(E229:T229)=16,"",SUM(T229,P229,L229,H229))]
U230 =1009 [=IF(COUNTBLANK(E230:T230)=16,"",SUM(T230,P230,L230,H230))]
U231 =36 [=IF(ISERROR(U229-U230),"",U229-U230)]
V229 =no value yet
V230 =1045 [=IF((SUM(E229)=0),"",E229)]
V231 =-1045 [=IF(ISERROR(V229-V230),"",V229-V230)]
W229-X231 = no value yet - but error checks are all the same as above
Y229 =no value yet [=IF(SUM(V229:X229)=0,"",SUM(V229:X229))]
Y230 =1045 [=IF(SUM(V230:X230)=0,"",SUM(V230:X230))]
Y231 =NEED VALUE [=IF(ISERROR(SUM(Y229-Y230)),"",Y229-Y230)]

It's hard to decipher which part of that post is not doing what you expect

It would be easier if you could post a sample book.

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