Loader for .NET packer

[SystemeD]

Hi all,
I'm trying to write a loader for a .NET packer which acts like that:

1 - Native code decrypts a .NET dll in memory and executes it
2 - The .NET dll performs some license checks and if ok loads the main .NET exe

Note: everything is packed together in one file

With my loader I would like to patch some bytes in the dll once it is decrypted in memory. The problem is how to be sure of the address to patch?
Thanks

PS: I can also patch the native code after the dll is jitcompiled but here I have the same kind of problem, the address to patch depends on where the compilation is made at runtime.