C API Callback Functions Excel4, Excel12
The Excel4 and Excel12 functions are provided to enable DLLs to call an internal Microsoft Office Excel worksheet function, macro sheet function or command, or XLL-only special function or command. All recent versions of Excel support the Excel4 function. Only Microsoft Office Excel 2007 and later versions support the Excel12 function. Both functions are provided in two forms:
A variable-length argument list form (Excel4/Excel12)
An array-of-arguments form (Excel4v/Excel12v)
Except for the way in which arguments are passed to these callbacks, the two forms are functionally equivalent. The basic concepts for both forms are fully described in Excel4/Excel12. Excel4v/Excel12v covers other issues about this form.