Dynamic editor dll linking?

Hello,

i have a situation where i'd like to have one external managed dll contain unityengine.dll functionality and/or unityeditor.dll functionality determined at runtime.

Right now i have a custom editor in one external managed dll, and i have my core code in another.

What i'd like to do is to be able to merge my code into one dll, however this presents a problem. obviously, when trying to run a build, the unityeditor.dll isn't present. Is there a better way (if at all) to do a runtime detection on whether my dll is executing in the editor and get a running instance of it?

this would need to work during runtime, NOT compile time.

Again. I would simply like to merge my assemblies into one and only execute my custom editor code if it's of course running in the editor.

Please advise?

thank you