There is something you're not telling us. Does this error occur before of after you enter the field? Are you using an imput mask? What are the charactaristics of the field you are adding? Are useing the SBT format, example la_armast[1, bi_invno]? Do you have a technicale reference manual.
SBT uses it's own flavor of VFP which is rather non-standard.
Bill Couture