Custom DAX Functions with Variables

Would be useful if you had the ability to create your own DAX functions that allows for variables to be inserted into the function.

I find that quite often I require a Base Measure that only subtly needs changing. Eg, Groups by a different dimension in a SUMMARIZE formula, or alternately uses a different SUM measure to produce a different result with the same manipulation of the rest of the DAX Formula.

This will allow for the Base Measure to be adjusted if a more effective solution emerges, rather than requiring a change for every single measure that the function has been applied to.