adding vlookup

im trying to created a worksheet that adds the number of days people are off in a year, i have come up with this formula as people can chage teams and therefore position in the worksheet,

=VLOOKUP(A18,Feb!A18:AJ161,35,FALSE)+VLOOKUP(A18,A18:AI162,34,FALSE)

the problem im having is that if the person has only joined the company that month its returning #NA error.

the code above is for march's total figures and a total todate figures. hope this makes sense. if not i can post an attachment any help would be much appriciated

does this work?

=Sumproduct(--(Feb!A18:A161=A18),Feb!AJ18:AJ161+AI18:AI162)

How about in AI5:

=SUM(SUMIF(Jan!$A$6:$A$35,A5,Jan!$AI$6:$AI$35),SUMIF($A$6:$A$36,$A$6:$A$35,$AH$6:$AH$35))

copied down.