Some functions are hidden by report studio dependant on the data source that is being used (relational or multi-dimensional).
An example is the function ‘running-total’. This function does not display when building reports from cubes (see below).
It is not necessary to do a complicated work-around to perform a running total on cubes.
The function can still be used by simply typing the function name into the data item expression window.
The function still validates and performs as expected to achieve the desired result.