Saving in Construction Set?

[Pterodactyl]

Hello, i've been playing oblivion for a while but have just started modding with the TES Construction Set and feel like a bloody idiot when using it.

 

My noob question is this:

I made a mod, and I want to go back and add things to it. My mod just adds a lame cave to Tamriel, and I want to possibly make the cave bigger or add more monsters to it. So i go into the construction set and click on data and select my mod/plugin thing only. Now, i edit my mod and do whatever I want and then i go to click save but it says that "File 'mytestmod1.esp' is a master file or is in use. Please select another file to save to."

 

What did I do that has brought this insanity upon my mod? :[ please help,

 

Pterodactyl

[The_Vyper]

Did you remember to set your mod as the Active File after you reloaded it in the CS?

[Hickory]

Make sure it's not being used by another application like Wrye Bash or OBMM, or your Oblivion Launcher. Close them all when useing the CS.