Plotting data with formulas that result in a blank or empty cell

Hello

I am trying to figure out how to create gaps in a line chart where the data is blank.  The data I am trying to plot is based on formulas, for example:  =IF(SUM(Calc!N5:N57)=0,"",SUM(Calc!N5:N57)).

I have the settings for the chart set to "show empty cells as gaps".  If I delete the formula the cell plots as a gap.  When the formula is in the cell it plots a zero.  I'm guessing "" may not be the best way to make a cell blank using a formula.

Thanks for any insight you may have.

SJP