Do you want to calculate the sum of all values in Plan_NumberOfUnits column when the date is before the slicer selection date(e.g. 1/17/2017)? If that is the case, create the following measures in your table.
I know this is old but I have exactly the same problem - I need to take the max value from the filter even if that is higher than the max date in the data set.
e.g. user selects data range 1st to 30th Jan, but the there were no sales on the 28th, 29th and 30th. I still want sales per day to be divided by the user selected range (30 days) and not the last date that fits in the range (27)