Excel has lots of built-in functions that do everything from summing up a column or row of numbers to loan repayments, statistics, engineering, trigonometry and so much more. Every now and again someone asks how they can create their own function as the one they want is either not on the list or they have a formula that they need to use regularly and it would be easier to have a function to call on when they need it. Sometimes it is because the formula they are using is either going to get too complicated or in the case of the IF function limited to the number of conditions it can have.
Custom functions can be made available to work in any workbook you have open or distributed to a group of people like colleagues or classmates.
Here in this video you will see how to create a custom function.