Revising and refining this question. I am at the point where I figured out how to calculate the difference between the first and last date in a range using LAST(). One snag I have run into is that my data also has a 'check' dimension that I want to display as a color and what is happening is that LAST() is returning true multiple times because it appears to be partitioning by the check dimension, so it is returning the last date for all the states of the check dimension.
The workbook attached illustrates the case. You can see that some entries in the Diff table have two numbers. If I remove the Check dimension from the color bin the table becomes what I want.
I think the solution lies somewhere in using the MAX function on date, since I only want the last value by date that corresponds to a given concept row to be used in my calc.
thanks much .. i feel like I am close here
Tritable.twbx 882.2 KB