NEXT FIELD error 1119 in CONSTRUCT

Hi, I've encountered the problem in CONSTRUCT .. NEXT FIELD option. When I run the following code I get the error in BEFORE FIELD section FORMS statement error number -1119 NEXT FIELD name not found in form ----------------- .4gl ------------------------ database tax main define scratch char(512) open window win1 at 3,3 with form "screen1" construct scratch on tbl.sname, tbl.lname, tbl.podr from s_screen1.sname, s_screen1.lname, s_screen1.podr before field lname if get_fldbuf(sname) is not null then next field podr end if end construct end main ---------------- screen1.per ------------------------- DATABASE tax SCREEN { fld1 :[A1 ] fld2 :[A2 ] fld3 :[A3 ] } TABLES tbl ATTRIBUTES A1 = tbl.sname, comments = ""; A2 = tbl.lname, comments = ""; A3 = tbl.podr, comments = ""; INSTRUCTIONS screen record s_screen1 (tbl.sname, tbl.lname, tbl.podr) delimiters " " -------------------------------------------------------------------------- Can somebody explain me what's wrong? I run OnLine 5, I-4GL v.4.10 Thanks in advance, Vadim