What I would do is access the string in the other sum functions and check for whatever you are looking for and proceed accordingly.  If you know the number of holidays or the max you could break the one shared string into many different variables, or you could put then in an a shared array, but the end result is always the same...you need to look at the variables to determine what the value is.  If it is just one or two values that you are looking at the for the other formulas, you might populate booleans (again shared )to be check by the other formulas...but it all the really.

 

Pick the option that you like the best.

 

HTH