How do add link a table for left list?

In my object, the main table is STOCK and under the environment tab, I linked the itmmaster table. When I write my code to get the itmmaster table linked, it will not link. Everything works when I use the STOCK table, but when I try to use the ITMMASTER table, it fails.. Here is the 4GL code:

Local Char FLTPCK (250)(4) : Raz FLTPCK
Local Integer I : I=0

FLTPCK(0) = "1=1"
FLTPCK(0) += "&[F:STO]STOFCY = '" + [M:SMO0]STOFCY + "'"
FLTPCK(0) += "&left$([F:STO]LOC,1)='1'"
FLTPCK(0) += "&[F:ITM]TCLCOD = '40001'"

Filter [F:STO] Where evalue(FLTPCK)
Fillbox [SMO1] GAU_CHE1
Filter [F:STO]

Can somebody help me? I've been stuck for a while and I have no clue on why the itmmaster won't link. 

Thanks.