reference field GV_regp-wrbtr unknown in the form

HI

am doing smartforms ,i declared a internal table it_regup in smartforms and bought data into it from table regup and looped it into gv_regup , while debuggind i can see the data in the tables, and i can display vblnr,xblnr,waers belnr but when i included dmbtr and wrbtr its throwing an error

reference field GV_regp-wrbtr unknown in the form

message ssfcomposer601

n a blank screen is comming what to do?

in syntax check its not showing any error

thanks in advance

regards

bhasker