excel-vba documentation: ユーザー定義関数（UDF）

Any UDF has a basic rule, you need to define it under FUNCTION procedure instead of a subroutine procedure (sub-procedure we generally use). Using the FUNCTION procedure, we can create UDF’s and can use them inside Excel as the general Excel functions s

Below we will look at a program in Excel VBA that creates a User Defined Function. Excel has a large collection of functions. In most situations those functions are sufficient to get the job done.