Pie Chart - Remove Legend labels that have no value

Hi

I have a table of data and some of the values are $-
A pie chart is linked to this data - I know how to make the pie chart ignore the $- in the data labels but I need to figure out how to make it disappear from the Legend as well ?

Anyone know how to do this?

Thanks

Thanks Andy - I have seen that before on another post but I cant really understand it and apply it to my spreadsheet...when I use the exact same formula as you have shown the legend labels still then just show as #NUM!