IIRC, there is one data type available in the 64 bit that is not available in the 32. So this would not be a problem if developing in 32 bit. Otherwise, some API's looking for 32 bit dll's might need to be adjusted. You would use ptrsafe with Access 64bit.
Code:
Declare PtrSafe Function RegOpenKeyA Lib "advapire32.dll" (ByVal hKey as LongPtr, ByVal lpSubKey As String, phkResult As LongPtr) As Long
I believe this is the code you want to use to test for Access 64bit.
Code:
#If Win64 Then
MsgBox "Win64 yes"
#Else
MsgBox "Win64 no"
#End If
for reference
https://msdn.microsoft.com/en-us/library/ee691831.aspx