Excel: How to Create a Custom Function with One Argument
Excel has lots of built in functions but sometimes it doesn't have what you want or perhaps you need to create a formula that uses lots of IF functions and it is either going to get confusing or you are going to hit the limit of the amount of conditions you are allowed. Here Gary Schwartz from http://www.jargonfreehelp.com shows us how.
Other useful tutorials:
How to turn a custom function into an add-in • Excel VBA - How to Create an Add-In f...