REGISTER.ID Function

REGISTER.ID(module_text, procedure, type_text)
https://support.office.com/en-us/article/register-id-function-f8f0af0f-fd66-4704-a0f2-87b27b175b50

module_text - The name of the DLL that contains the procedure (for Windows).
procedure - The name of the procedure in the DLL (for Windows).
type_text - The text string specifying the data type of the return value.

This function does not appear in the 'Insert Function' dialog box.
This function can be used on worksheets (unlike REGISTER), but you cannot specify a function name and argument names with REGISTER.ID.
You can also use the ordinal value of the function from the EXPORTS statement in the module-definition file (.DEF) although this must not be in text format.
You can also use the resource ID number although this must not be in text format.
The first letter of "type_text" specifies the return value. If the function or code resource is already registered, you can omit this argument.
If you are using a Macintosh then the function syntax is slightly different REGISTER.ID(file_text, resource, type_text). file_text is the name of the file that contains the code resource. resource is the name of the procedure in the code resource.

Returns the register if for the function called MyFunction.
=REGISTER.ID("Kernel32","MyFunction")