Creating a Time intelligence “External Tools” app for Power BI Desktop Top Posts.With the new Power BI desktop release (July 2017) comes a new DAX function called “SelectedValue”, this DAX function is a convenience feature to help you with working with selections.How can I return a NULL so these rows are simply left empty? Example formula below: =IF( = '', NULL, -) A small note, I am actually using Power BI Desktop however the engine accepts virtually all of Excel's formulas.