Charts

I have set up a reporting system and I have added permission levels so that different users can see different data. If i have a before sql query to restrict a user from viewing certain data the bar collum does not show the data (great) but where the data should be the number 0 is displayed and the legend still displays the title of the hidden collum. Is their a way of running an event to remove the data collum entirely so that instead of having 5 bars 2 empty it just shows 3 bigger bars and titles that match?