Take your old DLLs and add a compat_
prefix to them.
Basically rename your MyAppDataAccess.dll
file to compat_MyAppDataAccess.dll
.
Now go to the properties of your ActiveX DLL and set your project to have binary compatibility with the new compat_MyAppDataAccess.dll
, like below.
Now just build your DLL and deploy it.
It should work. If, in fact you binary compatibility would be broken as a result of your changes, then you'll get a warning stating that.