You got this error message if you referenced a variable that is currently undefined. For example if you tried to display the value of user variable A, when it doesn't have a value (possibly the contents were deleted by DelVar). You could also receive this message, if you try to display a calculator picture (RecallPic), and that picture currently doesn't exist. There are a lot of scenarios in which you can receive this error message. If you happen to get it, see if that variable has a value. If it doesn't then you need to give it one, before you can use it.