The main Function Wizard dialog allows you to enter the definition of the new add-in function. What do all these fields mean? Name - The name you enter here will be used as the name of the function visible in Excel and also as the name of the C++ function that implements the add-in function. Return type - The type of value that will be returned to Excel by the add-in function. In this case "Double" stands for "double-precision floating-point number". Category - When the function appears in Excel's Formula Wizard, it will appear under the category you enter here. Description - This description will appear in Excel's Formula Wizard. It will also be inserted into your C++ code as part of the function's header comment. You can also add an argument in this dialog box, select the argument type, name and description.