Dimitry,

Run the code from message#01684073. Watch your screen. Your REPLICATE(' ',10-LEN(ALLTRIM(REFERENCE))) is like REPLICATE(' ',10-LEN(REFERENCE)) for the determination of field length. This internally runs BEFORE filling the fields.

To make at as clear as possible how SELECT SQL works
1. It does a blind run to figure out field types and length. This run is not visible and gives no record in return. This run ignores ALLTRIM() So SELECT REPLICATE(' ',10-LEN(ALLTRIM(REFERENCE))) AS cField FROM .. is executed like SELECT REPLICATE(' ',10-LEN(REFERENCE)) AS cField FROM .. 10-LEN(REFERENCE) is like 10-15; equals -5
2. It runs to fill the result records, here the ALLTRIM() will be respected.
So your code errors out on point 1.

IOW. It does not matter how many signs you have in any record in the field REFERENCE. As long as the field length itself is greater then 10, your code must fail.

Just an other example

CREA CURSOR mycur (i1 I, c1 c(10))
INSERT INTO mycur VALUES (0,'')
INSERT INTO mycur VALUES (0,'c')
INSERT INTO mycur VALUES (0,'cc')
SELE ALLTRIM(c1) AS c1 FROM mycur INTO CURSOR cmycur
?LEN(cmycur.c1)

Why do you think cmycur.c1 has length 10? Because of the blind run.