Graphs in Excel

When a formula in a graph data range evaluates to a blank cell (i.e. “”), Excel takes it as a cero value. The line (or the bar) in the graph will show a zero value (and touch the x axis).
Is there a way to avoid this?
I want to use formulas in thedata range. In this way, the graph shows a line (or a bar) if data is available. If not, I want it to show nothing.
Thank you.