lookup error

[Dennis DIller]

I'm trying to add up some data and put the data in the proper month and year
from a check book file while sitting in the vendor file asking for the two 
digit year
Year   10   for 2010
the check file has a vendor id field(4)
and a field month & year it was written example 0210 for Feb. 2010 Field 
(14)
I have a auto index K with field 2 & 14 on this file
a dummy field tl that holds the vendor ID and month/year example  tl = 
BEV0210
Why do I get a error message on line 687 look up has not been performed
anyone help will be greatly appreciated
Denny

ytdloop *              If:      tj ge tk        'if tj get to 1310 return 13 
month 10th year
                        Then:      tj="01"{tf; tj=tj-"1"; tl=ti{tj; 
tk=tj+"1200"; 44=sa; sa=""; zz="1" ; return
                              If:
                          Then:     lookup ytd = decheck  k=tl   i=k -nx
 YTDLOP2    687  If:      not ytd or tj ne ytd(14)  'this add 100 to go to 
the next month 0110 +100=0210
                        Then:      tl=""; tj=tj+"100"; tl=ti{tj; zz=zz+"1"; 
close ytd; goto ytdloop
                          ■ If:     ytd and tj=ytd(14)    'this add the data 
put it the proper month
                         Then:     ttt[zz]=ttt[zz]+ytd(7); sa=sa+ytd(7); 
display; getnext ytd; goto ytdlop2
This work until there is a month with no entry example
bev0110            3,000   month1
bev0210            7,000   month2
bev0310            5,000   month3
bev0410             Look up is looking for bev0410 that record does not 
exist line 687 should be false  to goto bev0510

anyone have any input on this
Denny