Martina,
I do not know of a way to do this within OneClick. What I normally recommend is to create two CLI scripts:
One to find all of the models that are associated with the GC and set the isManaged attribute id 0x1295d and set it to No to put the models in main mode
The other to find all of the models associated with the GC and set the isManaged attribute id 0x1295d and set it to Yes to take the models out of main mode
Then, use cron of the Windows schedular to run the scripts at the times needed.
Joe