You can do this by right clicking on Value and select Quick Table Calculation>Percent of Total. Then, right click on it again and select Compute Using...>Table (Down).
Then, double click on Value from the data box (Measure Values should appear). Right click on the % of Total of Value on the view and select Edit Alias...
Hope this helps!
%of total based on sum.twbx.zip 10.1 KB