Automatically updating a record using count() of another collection

I have been looking at the docs and searching for videos on my problem, but I find nothing. I have a db called HPDASH where I have 2 collections, scripts and serverList. My problem is that I want to create a field for serverList that has the count() of the collection scripts. I have tried this:
db.scripts.insert([{name: 'local_script'}, {name: 'qidsloader'}])
db.serverList.insert({script_count: db.scripts.count() })
The problem is that when I insert another record to scripts, the data on scripts_count stays as 2. Is it possible to achieve this on MongoDB?