Once the first value for a plot has been defined, Metastock cannot plot nothing - if the formula evaluates to an invalid result (e.g. division by zero) it will still plot a line - usually at zero. I want to be able to define a null plot - i.e. to force Metastock to STOP drawing the plot until the formula says it should be drawn again. There is a way around it of sorts, and that is to have a second plot of the invisible style on top that covers up what you don't want to see. The problem with that is that this method takes up a lot of formula space because you effectively have to write it twice and tweak the send one! :( What I am looking for is the opposite of the 'IsDefined' and 'IsUndefined' functions - which are just logical operators that return a 1 or 0. I want to force an Undefined state so the plot will dissappear until I define it again. Let me know if this doesn't make sense. SteveD