FWIW, (I don't have 64 bit Office)

JKP has a very nice writeup

https://jkp-ads.com/articles/apideclarations.asp

and has links to the MS resources

Links

Of course Microsoft documents how to do this. There is an introductory article on Microsoft MSDN:
Compatibility Between the 32-bit and 64-bit Versions of Office 2010
That article describes the how-to's to properly write the declarations. What is missing is which type declarations go with which API function or sub.
Microsoft has provided an updated version of the Win32API.txt with all proper declarations available for download here:
Office 2010 Help Files: Win32API_PtrSafe with
I've used the MS links to update APIs to work with 32 or 64 bit Office